When shifting to Reverse, Service Traction Control and Service Stabil track lights come on?

When I shift in to Reverse the transmission has a hard shift and kind of lurches a little then I get a few lights that pop up on the dash and a message that says Service Traction Control. The doors are usually locking and unlocking while the transmission shifts and then when it all stops a "Service Stabil track" message comes on. I used a Zurich scantool and the Chevrolet ABS has code U2106-00 "Lost Communication with Transmission Control Module"

What could be causing this? I seem to recall a similar issue happening about 5 years ago. I don't remember exactly what was replaced because of language barrier between myself and the mechanic (my father in law's friend) so he mostly handled it.

Not sure if it matters but. I recently had to get a new Catalytic converter because the other one "went bad". The dealer gave me no explanation as to why it went bad and also didn't look into what could have caused it. I've also had both camshaft position sensors replaced within the last 5 years as well.