i had a problem with my ex-m1, it evidently took a hit during shipping from the prior owner, one channel would go out after the unit had fully warmed up playing music.
i emailed kinki in singapore, and the guy there was responsive... after some back and forth he said please send it to todd in texas, he will diagnose and fix... which i did, and which todd did (he is very sharp, found a cracked trace on the offending channel's input circuit board, fixed it up, send it back to me and all has been fine ever since