The card could have bad sectors on it or have corrupt data behind the partition. Even the best cards wear out and can go bad for other reasons. Check it with h2testw even if you think it's good just to be positive about that. Otherwise you may wind up chasing your tail needlessly
After this try a different power supply- most mini-USB phone chargers will deliver enough current for this. Also, how long does it run without power before shutting down? If it's only a few seconds when the settings say you should see more then the internal battery could be going bad.
I notice you say you've had the cam a few years. It's entirely possible it's simply on the way out- some component has gone out of spec now, a cold solder joint is finally letting go etc. Cams at this price point often give only a few years service before dying and even the best cams won't last forever. Just how it goes sometimes with anything electronic
I paid~$35 for my G1W-HC's and if they go 3 years I'll be happy; if they go 5 years I'll be amazed
Phil