95 f350 diesel trans problems

i know i know, its a common trans to give trouble, but i am stumped. the trans was rebuilt 4 times in the last month to ensure all was done i have receipts for all new parts from the trans shop. the truck would stall in reverse and buck hard into 3rd, it had a banks trans command on it, so i went down to banks and saw a tech who gave me a bypass shunt for the transcommand. the truck was awesome, no misshaps at all, i put about 60 miles on it with no problems, shut downs and restarts and all. then i stopped by the house, shut it down and when i came back and started it to leave i put it into drive and it started backing up. then i fumbled it into 1 and it went ok but only in first gear. i checked the fluid and the linkage, no problem found. i even disconnected the linkage and manually shifted it into drive, it still backed up in reverse instead. my question is, is it an internal problem? did the trans shop mess up perhaps? why was it ok all day first, then suddenly messed up? is it an ecm problem? i had a bronco with an ecm problem when you put it intop reverse and gave it gas it would lock up and stop the truck. i am so confused........