I agree that they probably didn't look for the cause. We haven't used the self clean mode since the last time Whirlpool came out and replaced the panel. (15+ years ago).Here is what I think likely occurred: There was one of those problems to begin with which caused the initial control to fail. The person that repair it the first time just replaced the part but didn't bother to find and correct the cause. The replacement control eventually suffered the same fate. This time they erroneously blamed using the self clean as the cause.
I do not know the temperature failure point of those relays (check with the relay manufacturer) but almost surly the thermal fuse would open well before those relays got hot enough to fail.
When the oven failed this time, there was no control panel thermal fuse to fail at p7-1; it was missing. That is how I found it from the previous time it was repaired (15+ years ago) as mentioned in previous posts back on January 15th.