Mango (GL-MT300N-V2) frequently looses configuration/connection

I’ve a Mango configured as an extender to bind a LAN-Only device (printer) into my WLAN via bridge.
The Mango is being switched on/off with the printer. However after some time it frequently looses its WLAN connection and is not more accessible. I’ve to reset and reconfigure manually every time.
This happened 5-7 time since beginning of this year.

There is at least one other user with another device who reports the same https://forum.gl-inet.com/t/ar-300m-lost-configuration/10425 so I assume it is a firmware problem, not a hardware problem.

Any idea how to resolve this issue? Perhaps by accessing it via USB-UART?

How far is Mango from the main router?
Alternatively, you could try lowering mango’s own WIFI rate to improve stability.

~5meter

That’s not the problem. It works for some time but then mango is no more accessible after booting. Long pressing the reset button and reconfiguring is all that work since the WLAN led is off then and it has no connection anymore. Seems like mango forgets the WLAN credentials