We have been using the M7300 mifi on a 4G network for two years now.

Two days ago, we were still connected to the internet, but only received 1 kb/s. If we selected a 3G network, it worked even better (100 kb/s)

After having tried almost everything I removed the battery yesterday and put it back, after which it worked perfectly again.

This morning, it had again lost connection and removing and returning the battery helps every time, but only for a couple of minutes.

Every time the reception is really good, I can ping the mifi and ping google, for example. 

Normal reboots or resets don't help, neither does changing any of the settings.

I have checked the placement of battery and SIM, but it all seems fine.

Any clue what this could be?