This might be a dumb question, but I assume Long Generic Test is the same as Long DST? Long Generic was the only "long" test I had in SeaTools, though it does have both the Short DST and Short Generic options...
I forgot to mention in my OP that I did check & reconnect the cable before running into the disk damage/full error when trying to format. It appeared fine, but I guess that doesn't rule out a cable issue...though I thought SeaTools would give a
"bad cable" error code if that were the case?