Good day,
may be some of you have encountered this issue with MUDI (based on EP06-E) when it drops modem connection occasionally (several times per day or once per day). It takes time until it restores that connection (~5 mins) alternatively manual reboot also helps.
I have pulled-out system-log and I see that usb interface seem broke and it tries to reset it.
I’ve tried to upgrade to the latest firmware (3.203 => 3.211) but the same happens 
Any experience with this may be or is it just my bad luck with faulty hardware?
----syslog—
Wed Jan 12 19:25:55 2022 kern.err kernel: [ 9965.360703] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.393714] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.427716] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.461704] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.494713] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.494727] usb 1-1-port1: Cannot enable. Maybe the USB cable is bad?
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.528721] usb 1-1-port1: cannot disable (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.562702] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.596718] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.630717] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.668704] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.701720] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.701734] usb 1-1-port1: Cannot enable. Maybe the USB cable is bad?
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.735731] usb 1-1-port1: cannot disable (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.771698] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.806711] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.840710] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.874701] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.907718] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.907731] usb 1-1-port1: Cannot enable. Maybe the USB cable is bad?
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.941719] usb 1-1-port1: cannot disable (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9965.975703] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9966.010723] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9966.044714] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9966.079806] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9966.113802] usb 1-1-port1: cannot reset (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9966.113817] usb 1-1-port1: Cannot enable. Maybe the USB cable is bad?
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9966.147481] usb 1-1-port1: cannot disable (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9966.181809] usb 1-1-port1: cannot disable (err = -71)
Wed Jan 12 19:25:56 2022 kern.err kernel: [ 9966.216242] hub 1-1:1.0: hub_ext_port_status failed (err = -71)
Wed Jan 12 19:26:00 2022 user.debug : MCU SIM ERROR
Wed Jan 12 19:26:09 2022 user.debug : MCU SIM ERROR
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.096277] ------------[ cut here ]------------
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.096336] WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:320 dev_watchdog+0x164/0x274
Wed Jan 12 19:26:10 2022 kern.info kernel: [ 9980.096342] NETDEV WATCHDOG: wwan0 (qmi_wwan): transmit queue 0 timed out
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.096345] Modules linked in: ath9k ath9k_common rt2800usb rt2800lib pppoe ppp_async ath9k_hw ath10k_pci ath10k_core ath rt2x00usb rt2x00lib pppox ppp_mppe ppp_generic option nf_nat_pptp nf_conntrack_pptp mac80211 iptable_nat ipt_REJECT ipt_MASQUERADE ebtable_nat ebtable_filter ebtable_broute cfg80211 xt_time xt_tcpudp xt_tcpmss xt_statistic xt_state xt_recent xt_nat xt_multiport xt_mark xt_mac xt_limit xt_length xt_hl xt_helper xt_hashlimit xt_ecn xt_dscp xt_conntrack xt_connmark xt_connlimit xt_connbytes xt_comment xt_TCPMSS xt_REDIRECT xt_LOG xt_IPMARK xt_HL xt_FLOWOFFLOAD xt_DSCP xt_CT xt_CLASSIFY wireguard usb_wwan ts_fsm ts_bm slhc sierra_net sierra rndis_host qmi_wwan nf_reject_ipv4 nf_nat_tftp nf_nat_snmp_basic nf_nat_sip nf_nat_redirect nf_nat_proto_gre nf_nat_masquerade_ipv4 nf_nat_irc
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.096544] nf_conntrack_ipv4 nf_nat_ipv4 nf_nat_h323 nf_nat_ftp nf_nat_amanda nf_log_ipv4 nf_flow_table_hw nf_flow_table nf_defrag_ipv4 nf_conntrack_tftp nf_conntrack_snmp nf_conntrack_sip nf_conntrack_rtcache nf_conntrack_proto_gre nf_conntrack_netlink nf_conntrack_irc nf_conntrack_h323 nf_conntrack_ftp nf_conntrack_broadcast ts_kmp nf_conntrack_amanda iptable_raw iptable_mangle iptable_filter ipt_ECN ipheth ip_tables huawei_cdc_ncm ebtables ebt_vlan ebt_stp ebt_redirect ebt_pkttype ebt_mark_m ebt_mark ebt_limit ebt_among ebt_802_3 crc_ccitt cp210x compat_xtables compat cdc_wdm cdc_ncm cdc_ether cdc_acm xt_u32 fuse sch_teql sch_sfq sch_red sch_prio sch_pie sch_multiq sch_gred sch_fq sch_dsmark sch_codel sch_cbq em_text em_nbyte em_meta em_cmp act_simple act_police act_pedit act_ipt act_gact act_csum
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.096737] libcrc32c act_connmark sch_tbf sch_ingress sch_htb sch_hfsc em_u32 cls_u32 cls_tcindex cls_route cls_matchall cls_fw cls_flow cls_basic act_skbedit act_mirred xt_set ip_set_list_set ip_set_hash_netportnet ip_set_hash_netport ip_set_hash_netnet ip_set_hash_netiface ip_set_hash_net ip_set_hash_mac ip_set_hash_ipportnet ip_set_hash_ipportip ip_set_hash_ipport ip_set_hash_ipmark ip_set_hash_ip ip_set_bitmap_port ip_set_bitmap_ipmac ip_set_bitmap_ip ip_set nfnetlink ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6t_NPT ip6t_MASQUERADE nf_nat_masquerade_ipv6 nf_nat nf_conntrack nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables ip6t_REJECT x_tables nf_reject_ipv6 GobiSerial usbserial GobiNet usbnet ip6_udp_tunnel udp_tunnel tun vfat fat ntfs nls_utf8 nls_iso8859_1
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.096909] nls_cp437 sha1_generic ecb uas usb_storage uhci_hcd ohci_platform ohci_hcd ehci_platform sd_mod scsi_mod ehci_hcd gpio_button_hotplug ext4 mbcache jbd2 exfat phy_ar7200_usb phy_ar7100_usb usbcore nls_base usb_common mii aead crypto_null cryptomgr crc32c_generic crypto_hash
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.096995] CPU: 0 PID: 0 Comm: swapper Not tainted 4.14.241 #0
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097000] Stack : 805e0000 8059bce8 00000000 00000000 8056877c 87c07e04 805c9e0c 805c9a27
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097025] 80564860 00000000 80723670 00000140 805d5074 00000001 87c07db8 8ff2ab35
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097048] 00000000 00000000 80720000 00007d70 00000000 00000000 00000001 00000000
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097070] 00000187 2e99765c 00000186 80740000 00000000 00000009 00000000 80595b98
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097093] 803ae9d0 00000140 805d5074 805d5034 00000003 00000000 00000000 80720000
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097116] …
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097123] Call Trace:
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097154] [<8006aafc>] show_stack+0x58/0x100
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097196] [<80085430>] __warn+0xe4/0x13c
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097207] [<800854b8>] warn_slowpath_fmt+0x30/0x3c
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097234] [<803ae9d0>] dev_watchdog+0x164/0x274
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097267] [<800bfbcc>] call_timer_fn.isra.26+0x24/0x84
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097277] [<800bfda0>] run_timer_softirq+0x174/0x1ec
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097303] [<804c03e8>] __do_softirq+0xe8/0x2bc
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097314] [<80291ab0>] plat_irq_dispatch+0xc0/0x120
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097324] [<800658f8>] handle_int+0x138/0x144
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097332] [<80065780>] __r4k_wait+0x20/0x40
Wed Jan 12 19:26:10 2022 kern.warn kernel: [ 9980.097343] —[ end trace 5c64d3f88c2157d1 ]—
Wed Jan 12 19:26:18 2022 user.debug : MCU SIM ERROR
Wed Jan 12 19:26:28 2022 user.debug : MCU SIM ERROR
Wed Jan 12 19:26:37 2022 user.debug : MCU SIM ERROR
Wed Jan 12 19:26:46 2022 user.debug : MCU SIM ERROR
Wed Jan 12 19:26:50 2022 daemon.err gl_monitor[3210]: Killed
Wed Jan 12 19:26:50 2022 daemon.err gl_monitor[3210]: Error opening serial port - No such file or directory(2).
Wed Jan 12 19:26:50 2022 daemon.err gl_monitor[3210]: Error opening serial port - No such file or directory(2).
Wed Jan 12 19:26:51 2022 daemon.err gl_monitor[3210]: Error opening serial port - No such file or directory(2).
Wed Jan 12 19:26:51 2022 daemon.err gl_monitor[3210]: Error opening serial port - No such file or directory(2).
Wed Jan 12 19:26:51 2022 daemon.notice netifd: modem_1_1_2 (31124): Stopping network modem_1_1_2
Wed Jan 12 19:26:52 2022 daemon.notice netifd: modem_1_1_2_4 (5320): udhcpc: received SIGTERM
Wed Jan 12 19:26:52 2022 daemon.notice netifd: Interface ‘modem_1_1_2_4’ is now down
Wed Jan 12 19:26:52 2022 daemon.notice netifd: Network alias ‘’ link is down
Wed Jan 12 19:26:52 2022 daemon.notice netifd: Interface ‘modem_1_1_2_4’ has link connectivity loss
Wed Jan 12 19:26:52 2022 daemon.notice netifd: Interface ‘modem_1_1_2_4’ is disabled
Wed Jan 12 19:26:52 2022 daemon.warn dnsmasq[3154]: no servers found in /tmp/resolv.conf.auto, will retry
Wed Jan 12 19:26:52 2022 user.notice root: modem_1_1_2 real ip miss
Wed Jan 12 19:26:55 2022 kern.err kernel: [10025.203697] qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Wed Jan 12 19:26:55 2022 kern.err kernel: [10025.203713] qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Wed Jan 12 19:26:56 2022 daemon.notice netifd: Interface ‘modem_1_1_2’ is now down
Wed Jan 12 19:26:56 2022 daemon.notice netifd: Interface ‘modem_1_1_2’ is setting up now
Wed Jan 12 19:26:57 2022 daemon.notice netifd: modem_1_1_2 (31390): Waiting for SIM initialization …
…
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