Question about Huawei E5576-320 Mobile wireless network equipment

Yup, I have the same problem.
Works wonderfully, suddenly no internet access.
WLAN sometimes remains without internet and in other cases the WLAN also disappears.
When I try to switch the thing off it kind of "bucks", the ON/OFF switch doesn't really react as it should.
Maybe the microcontroller has stumbled, this can happen when external disturbances occur, e.g. from the mains adapter, which is constantly connected.
I tried using a different mains adapter and am now waiting to see what happens.
By the way, the SIM is the one from Digital Republic.

It is powered by USB, and is a rechargeable battery with a battery life of approximately 6 hours when in use.