Off the hop, my guess would be inadequate cooling of an electronic component....and the primary suspect would be the EMM since that has just been worked on. That is just my guess from the chronology.
Two caveats:
1) I have no idea what prompted the work on the ECC....it may not even have been the root cause of whatever issue that it was.intended to solve. So there may be a deeper problem.
2) I have limited exposure to Ficht O/Bs, so am over my head already.
Happily, there are some Ficht experts around who will likely chime in.