RTL510 powers off soon after powering on

My RTL510 is having problems ... on the past few rides it won't stay powered on.

It takes a while to power on and, after being connected for a few minutes, powers off and disconnects.

I'm worried that it's the physical power button.

Granted, the past few rides have been very damp.  I wonder if the seal is compromised?

Any suggestions on an approach?  Or do I just write it off and get a new one?