Is my puck dead? (blinking red, cannot connect)

I've got 2 pucks.

1. I've replaced their batteries and updated to firmware v97.
   
2. I've uploaded same code via Web IDE.
   
3. One puck is happy and working all the time.
   
4. The other puck, after ~2-3h, will start blinking red.
   
5. It advertises as "Puck js XXX" instead of my name (which means it's reset itself and not running my code)
   
6. When trying to connect via Web IDE, it shows up on the list but then "error connecting" pops up.
   
7. Nail-reset doesn't help.
   
8. Taking out battery and reinserting after 1min allows to connect again, re-upload code.
   
9. After ~2-3h, it will start blinking red again.
   
   

What can I do?