A word from experience: an extender card can introduce noise, which can lead to observations of self-induced problems due to the introduced noise. I don't think

A word from experience: an extender card can introduce noise, which can lead to observations of self-induced problems due to the introduced noise. I don't think this is the case for your situation, but symptoms the runt edges you observed could be caused by the extender. Also, I have on occasion observed the magic of an extender card causing a flaky card to function properly. If you get stumped, you might want to depopulate some non-essential cards to open up a space to get your hands and probes on the card under investigation, while it is directly plugged into the slot. Excuse me, I mean get your hands and probes in there while the system is powered off.