Garmin OTR-800 stuck on "Dancing Triangle (pyramid?) Screen"

I've had an OTR-800 Trucking GPS for a few years now. I keep it updated regularly. I've had problems for the last year or more, especially at boot-up.

The unit boots up and defaults to a car profile. When I change it to one of the three profiles I created and use (Bobtail, 53' trailer, or pups), it goes to the dancing triangle screen, and stays there for an excessive amount of time. Just to see, one time I let it go on for over 40 minutes in this state. Most times it will eventually come out of this screen and be ready to use. But it can go on for long periods.

Sometimes a reboot or two will resolve this. It seems to be particularly successful if during the reboot, it goes back to where the black & white picture screen appears during boot-up (a picture of a tractor-trailer.)

Most of the time, this problem is confined to changing the profile at startup. But I have had occasions where it has gone into the dancing triangle spontaneously while driving. When that happens, suddenly I have lost all directions. While most of the time that wouldn't be a problem -being on the open road- I had it occur last month while I was driving in the L.A.- Ontario area, going to a new location I had never been to before. A mile or two before taking an exit, I lost all guidance. I had to blow past the exit a few miles until I could find a safe place to pull over, and recover the GPS.

Any ideas on what is going on here, and how to resolve it?