1996 Dodge Caravan tranny sticks in second gear

Have a 1996 Dodge Grand Caravan. Few months ago my van started staying in second gear while driving. Thought tranny problem, and limp mode BUT if you shut it off and restart, it shifts properly. Had it scanned at a tranny place and they said broken wire somewhere. Took a whole afternoon and traced and checked EVERY wire, fuse, fuse panel, and all connections. Could not find a broken wire anywhere. Have been driving it like this ( soon as we see RPMs at 2500 0r 3000 at 60-70 kph -- put it in neutral and restart and RPMs drop to 1500) since the fall. We are seniors on disability and cannot afford to take it in for them to try different things till they find the problem. Hubby has been a mechanic for many years but this has him stumped. He was wondering what the possibility is of the problem lying in the computer as the shifting can be rectified almost EVERY time with a restart. Seems like a connection issue of some sort just not sure where. Can you advise please?