Preamp/interconnects cause amp problems?

@dletch2 he did confirm the issue then repaired what was shorted and sent it back.  When I sent it back again he confirmed it happened again but couldn’t see what the cause was. So he pulled
and replaced the boards and the power supply. I’ve not paid a dime so far and I did offer to pay some shipping but he refused.

I just don’t want this to happen yet again because of something on my end. 

@dletch2 that was my thought as well. I just want to be sure. I haven’t popped a speaker yet and don’t want that streak to end

Just because the dealer could not find anything does not mean there is no problem. case in point, I bought a used preamp which had been at the mfg's service center for an issue which was supposedly fixed. The seller had it shipped directly to me. When I got it and hooked it up, the right channel quit working. Changing tubes didn't help. When I called the seller, he was shocked and said that it was the same issue he had sent it for repair. However when talking with the mfg, she too had left it running for a week trying to ;locate the issue and found nothing. I sent it back to her and declined the sale. Anyway, I learned later from the seller that it was a resister gone bad.

Some things happen like that and when your car has an issue that never shows when you take it to the mechanic. Life, I guess. The frustrating part

What model amp is this? Was everything OFF, not standby, that is connected to the amp when popping started? When you turn the amp off and then on again, has the preamp been on the whole time?