The Wonders of Micro Elecronics, I always wonder how they solder those flexible circuits without burning anything.
I recently opened up an expensive sports watch and found a single blob inside on a flexible circuit connecting to the lcd display.
Sprayed the whole thing with 94% surgical alcohol and let it dry overnight, new battery and it was good to go.
After a few years the rubber seals perish and sweat gets inside causing problems.