Clean and reapply thermal paste?  I had a hashing board on an S3+ that started running hotter than other S3+ hashing boards and although I lowered the voltage and frequency and after a cold restart seemed okay was dead the next morning.  Still dead.  Signal missing on if I recall correctly, pin 13 of the ribbon cable.  If I had repasted immediately perhaps I could have saved the board.  On the other hand it might be that if a chip is going it's going to go repasting or not.