There is a wealth of knowledge here. https://jestineyong.com/audio-restoration-repair-bose-wave-music-system-awrcc1-awrcc2-awrcc7/
Main premise is capacitors age and go out of tolerance. I suspect maybe a few in power supply stages would cause erratic behaviour. (don't need to replace them all) China blesses us with low cost ESR meters if high end gear is out of reach. This video was useful https://www.youtube.com/watch?v=snuJdw60ueg. (maybe play at 2x speed and skip as necessary)