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If the same thing happens with external or internal battery power, then I think it's not a matter of the power source causing it, at all.
Why not try updating it with Garmin Express? that often cures these sort of problems.
When dealing with an update for your Garmin device, it is best to simply download, install, and use Garmin Express.
and (if you have a Windows PC) click on the big blue Download button at center bottom of the page. (If you have an Apple, click on the nearby Download for Mac link.) And download Garmin Express' installer to your computer, save it, then double-click upon it to install Garmin Express.
Then start the program, Garmin Express. Then connect your Garmin device. Then use Garmin Express to update your device.
(If this helps with the problem and answers your question, please rate my answer. If there are any further problems, please Reply and let me know, and tell me how old the Garmin device in question is measured from its date of purchase ... and I'll offer further advice. Thanks.)