@MicT 

Hi, thank you very much for the feedback.

Upon checking, your current firmware is not allowed to downgrade to previous firmware. 

Regarding the unstable issue, please confirm if only WiFi connection is unstable, or LTE connection unstable, please refer to the following guide to troubleshoot WiFi disconnecting issue:

https://www.tp-link.com/en/support/faq/3416/

  @MicT 

1. When the problem happens, Wi-Fi is connected but no internet access? will it recover automatically or you have to do something to get it working again?

2. When the problem happens next time, please don’t reboot the MiFi device, try to login the web interface, send us screenshot of Status page and Advanced->Dial-up->Dial-up Settings page, then save a system log file on Advanced->Device->System Log page and let us know the specific time of the issue.

3. How often does the problem happen? Was it working fine and stable before?

4. If you insert the same SIM card into another 4G device and use for some time at the same location, will the LTE connection be stable or not?