TorqShift Tow/Haul Shift Problems

[JABECO]

Transmission is having trouble shifting out of 1st, it is like it goes to neutral, then goes into 2nd, no grinding, or noises, then the TOW/HAUL light starts flashing, I turn the engine off then back on and it goes away. This only happens when I have just been in reverse and had to back up any harder than idle speed. Otherwise it shifts fine. Then when I was pulling a trailer for the first time since the issue came about and was in tow/haul mode and when it tried to downshift to slow the truck down it failed and started flashing again. Ford shop says the code reads a "shifter selenoid failure", but can't explain why it only happens after a "hard" reverse or in tow haul mode. Any help?