Last days I used the Zyxel was a nightmare, loosing connection with Sosh (Orange) every few minutes (B20+B28 only with a correct SINR). And my script was only able to reboot the Zyxel as expected, but a router rebooting every few minutes is not a viable solution neither ;-) I finally revert to my old small yet robust Alcatel router and decided to wait until my next stay.

After a long search, I found a working LTE modem update file from version EG18EAPAR01A08M4G to version EG18EAPAR01A11M4G. The update file I received from tabor.tang-Q does not work. It differs in file weight, it is 104 MB, while the upgrade/downgrade file is 40 MB. I've read the thread in your link but it's quiet unclear for me: which firmware do you mean? I've tried both V1.00(ABQV.3)C0 and V1.00(ABQV.2)C0 with same issue, no difference.