Thanks very much, quite interesting alternate issue to check, and I will certainly try a thorough contact cleaning of my Pitfall II cart contacts with isopropyl alcohol before putting my 7800 under the knife.
However, the 2002 post I linked to did specifically mention Pitfall II, and furthermore, the OP in that post, @Tifany stated that after doing the hack, Pitfall II worked. Could it be a coincidence? @Tifany do you remember any details of that fateful day >17 years ago and have any opinions here?