Devices signal transmission suddenly breaks off

Hey.

We have a problem that we can't explain. A device suddenly breaks the connection off during the drive. You need to send a SMS back into the mobile network.
At the way back in the same area the signal is fine...

We use different devices from different manufactures - same problem

Has someone an idea where I can search for the problem?

thanks in advance

Is there any reason this topic is under server forum instead of devices? It sounds like device issue. Also, you should probably mention the device model.

ok Thank you.I posted in server because its different devices of different manufactures:

For example:
Teltonika fmb001
LK208