Garmin Oregon 600 behaving badly

After years of running flawlessly, recently, roughly a minute after turning on, the unit starts acting as if it had a mind of its own, or as if someone else had hacked into it. The screen change rapidly as if someone were touching it, but I'm not. It stops responding to my touch and sometimes stops acting on its own, too. It really looks like it's possessed. Never returns to normal unless I turn it off. Updating the software to version 5.60 didn't help. Resetting to defaults didn't help.

 

Thanks for replying! Stable when connected via USB to PC, able to send files back and forth, but cannot test other functions in that situation. When connected via USB to a simple charger, after 30-60 sec the screen starts jumping around from menu to menu or the map starts jumping from place to place, zooming in and out. I used it over the weekend to successfully generate a 7-hr gpx track but had to start the track quickly after turning on, and hope it got saved when I turned off the power. BTW, I always take the batteries out after use because otherwise they seem to run down. Could that have been a mistake? Is there an internal battery that needs to be replaced, like the one in my digital camera? I've been using Li batteries, but Alkaline makes no difference. Screen is not cracked or even scratched. Bought 9/2016.

 

Called Garmin today and the fellow suggested the hard reset using the power and user buttons, which didn't help. The hard reset put the touch screen sensitivity to "high" but lowering it to normal didn't help. They offer no repair services. I ordered the "LCD Display Touch Screen Digitizer Replacement for Garmin Oregon 600 GPS-Repair Part" from srjtek through Amazon for $77.