I am having the same issue as you guys. One cta goes to 120c right away and shuts down.  it was working for for the past 3 months.   the other CTA runs amazing over 800gh all the time
the "bad" one always ran hotter. i replaced the paste about 4 times now and like 4 cores go to the sky and it stops. at its different ones just seems like something is shorting out or i dont know what the hell is happing.  any input would be great.  i used ic diamond themal paste on all chips the "good booard temp are way down and it hashes amazing the "bad board is still HOT!

edit did some tinkering. found that letting the board cool down and then just start the one sounds like a fan in one of the pumps is ticking...   also found that the "out" side of both cores on the "bad board" are really hot and the "in"side is cold. On the "good" board both side are equally Warm cound it be a pump issue? both pumps show speed but not as fast as the other board.  if the fins inside the pump broke off the the pump would stiill spin just be clogged/not going anyhting?  im really tring to figure this out.    already had one of the power blocks that the soldered on the board break off that's why i opened it up in the first place. fixed that and now this heat/power/idk/short issue