08 Aero V6 Stability Control Warning followed by hard shift and stuck in one gear

Happened once a a few months ago , but 3 times yesterday. While driving the Stability /Traction control malfunction warning pops up, car stays in what ever gear it happens to be. Then when starting anew the shiftt into drive is a very harsh THUNK and stays in first. I did try disconnecting battery and reconnecting but that fix seems to only last a little while.
Oddly, when not happening, the engine shifts smoothly as can be .

155K Miles

Thoughts? Ideas?

Thank you as always