This could have many causes, including some of the ones you mention. You could try:
1) Make sure it is fully dry and at room temp before powering up. This applies to all electronic gear.
2) Open the unit and check that the battery is present and has not come loose in its socket. If it looks OK, consider replacing it. You will need to do a "clear everything" if you move or replace it.
The BADALG message fixed in 3.1 was a spurious report of a corrupted program – real corruption (such as from a bad battery) will give this report correctly.
Beyond this the unit probably needs to come home for service.