Trans slipping after waterpump replaced?

Hey all, I had my 2011 T&C in the shop for water pump and serpentine belt replacement 3 weeks ago. I noticed it felt a little shaky at start up after the repair. Now all of a sudden the transmission is slipping. No check engine light yet. Could this have anything to do with the recent repair?

Backstory- I did have a check engine light about a year and a half ago (P0740- Torque converter) Took it to trans shop, he topped off the fluid and everything was good. About 9 months later, same check engine light code came back. Took it back to trans shop, he said likely rebuild, they couldn't see any issues. Light went off on its own and hasn't been on since (5-6 months ago). Car was driving fine when I had check engine light. Didn't have any signs of trans issues before water pump and belt were replaced.

I've been told the trans fluid is finicky on T&C's, is that true? I've had mechanics tell me it's been overfilled & underfilled. I'll add- the mechanic who told me it was overfilled, underfilled it. It was after he did a repair that the check engine light came on initially. I brought it to trans guy, who said fluid was low.

Any insight appreciated!