Our of curiosity, does your 05 still have the original battery? It it has a white top, that indicates it is original. Batteries that are starting to go south can cause a lot of weird problems with these cars, that is why it is best just to change them out every few years to avoid being left in the lurch.

Certainly a lot cheaper to replace the battery than some of these expensive components, like the shifter assembly.

Did they get any transmission codes during your two repair cycles? This would be from the TCM or Throttle Control Module.

You could be in limp mode, however, I am not sure that when that happens if codes are generated. A reputable dealer should be able to figure this out.

Finally, yarn on that dealer that charged you 1800 Somolies for nothing. Sheesh. Good luck and keep us posted.