Bought a GL-MIFI (GLZT_MIFI_v2.6.3 printed on the board) with EC25-EFA-512-STD modem. Worked fine at first, but after a week or so the modem would not connect to the network anymore - on network registration it would disappear from the USB bus and then reappear again (without having registered). Reflashing original firmware and resetting to factory defaults did not fix anything. After some more time, it will not even detect the SIM card anymore. Everything else beside the modem - LAN and WiFi - works fine. Tried two different SIM cards, which both work fine in another modem, so that’s not the problem.
Any suggestions for what else can be done?