2004 Freightliner M2 (106) truck. Intermittent check trans / limp mode question

I’m in 6th gear (auto mode) Allison 3000. At exit ramp with EB ON it helps slow truck down (in 4th). It stops, but sometimes upon giving gas, check trans light ON, stuck limp mode in 6th gear, have to shut truck off and restart, and then I can get through intersection. But now engine overheating. So, is the TC stuck OPEN or ClOSED ? Took to local Allison (Ocala) and they see the trouble code, but after several test drives at $90 hr they don’t see firsthand the problem ! So they refresh the tran computer sofware and $700 late I’m out the door, a week later, same problem again (limp mode in 6th gear and overheating).
Thanks