GL-MT300N-V2 : lighttpd (fastcgi.server) error

I upgraded to the firmware of openwrt-mt300n-v2-3.012 version.
But, the web is not accessed after upgrade.
I checked the error log.

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root@GL-MT300N-V2:/tmp# cat /var/log/lighttpd/error.log
2019-01-15 07:56:15: (server.c.1412) server started (lighttpd/1.4.48)
2019-01-15 07:56:15: (server.c.1441) WARNING: unknown config-key: url.redirect (ignored)
2019-01-15 07:56:18: (gw_backend.c.331) child exited: 255 unix:/tmp/html.socket-0
2019-01-15 07:56:18: (gw_backend.c.478) unlink /tmp/html.socket-0 after connect failed: Connection refused
2019-01-15 07:56:18: (gw_backend.c.331) child exited: 255 unix:/tmp/html.socket-0
2019-01-15 07:56:18: (gw_backend.c.331) child exited: 255 unix:/tmp/api.socket-0
2019-01-15 07:56:18: (gw_backend.c.478) unlink /tmp/api.socket-0 after connect failed: Connection refused
2019-01-15 07:56:18: (gw_backend.c.331) child exited: 255 unix:/tmp/api.socket-0
2019-01-15 07:56:19: (gw_backend.c.478) unlink /tmp/api.socket-0 after connect failed: Connection refused
2019-01-15 07:56:19: (gw_backend.c.478) unlink /tmp/html.socket-0 after connect failed: Connection refused
2019-01-15 07:56:20: (gw_backend.c.331) child exited: 255 unix:/tmp/html.socket-0
2019-01-15 07:56:20: (gw_backend.c.478) unlink /tmp/html.socket-0 after connect failed: Connection refused
2019-01-15 07:56:20: (gw_backend.c.331) child exited: 255 unix:/tmp/html.socket-0
2019-01-15 07:56:20: (gw_backend.c.331) child exited: 255 unix:/tmp/api.socket-0
2019-01-15 07:56:20: (gw_backend.c.478) unlink /tmp/api.socket-0 after connect failed: Connection refused
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I checked fastcgi program.
But, api is terminated immediately.
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root@GL-MT300N-V2:/www# ls -la
drwxr-xr-x 4 root root 120 Nov 19 2018 .
drwxr-xr-x 1 root root 0 Jan 1 1970 …
lrwxrwxrwx 1 root root 35 Jan 15 2019 api -> /usr/share/glweb1/bin/gl_fcgithread
drwxr-xr-x 2 root root 38 Jan 15 2019 cgi-bin
lrwxrwxrwx 1 root root 33 Jan 15 2019 favicon.ico -> /usr/share/glweb1/web/favicon.ico
lrwxrwxrwx 1 root root 29 Jan 15 2019 html -> /usr/share/glweb1/bin/gl_html
-rw-rw-r-- 1 root root 495 Jul 26 2018 index.html
drwxrwxr-x 4 root root 49 Jan 15 2019 luci-static
lrwxrwxrwx 1 root root 25 Jan 15 2019 src -> /usr/share/glweb1/web/src

root@GL-MT300N-V2:/www# /www/api &
root@GL-MT300N-V2:/www#
[1]+ Done(255) /www/api
========================================================

Please let me know what’s wrong.

@JamesIm
This is a bug in the old version. You can upgrade the software version 3.025 or 3.102. It is better not to keep the configuration upgrade.
3.025
https://dl.gl-inet.com/firmware/mt300n-v2/v1/
3.102
https://dl.gl-inet.com/firmware/mt300n-v2/testing/

Thank you to reply.
But I actually downgraded the firmware from 3.025 to 3.012.
I have to use firmware of 3.012 version because 3.025 version takes up more storage space than 3.012 version.
Can you send me the fixed 3.012 version firmware or binary files?
Or can you tell me another way?

@JamesIm
Compared with the changes from version 3.012 to 3.025, it is not a simple package update to solve, so it is recommended that you delete some packages on version 3.025

You can just hold the reset button for 10 seconds to clear your settings and it should work.

The problem may be caused you keeping the settings of a new firmware and used them in the old firmware.