Its not the 470Uf cap unless it was in backward.
The problem from my analysis is that anyone running the TDA2822 on 12V is at risk.
The parts max operating voltage is 12V!!! Thas straight from the data sheets of three
different vendors. Likely some can stand more but not guaranteed. Most 12V gell batteries
freshly charged are 13.8 and even after surface charge is leveled off its 12.6.
It would be better to run it at some lower voltage as its was designed for use at 1.8V to 12V.