Transmission shifting problems after hosing engine bay

[Bumblebeebum]

I own a 2012 RS V6LFX auto trans ~88k mi (bought used 1.5 yrs ago). I took it to a local mechanic for a P0191 with "Service Stabilitrak ! Engine Power is Reduced" DIC message and stumbling/almost stalling. There was also a P0442 immediately prior, thought they may be related but who knows. I replaced gas cap and purge solenoid valve first but the P0191 was still there and they diagnosed and replaced the fuel rail pressure sensor and cleared codes. Seemed okay after.

After I took the car home, it started smelling of gasoline real strong inside the cabin esp. when the HVAC was on. I took it back and they said it was residual and hosed off the engine bay and underside and ran it for a while and that took care of the fuel smell...

But, when I got in and put the car into drive, it bucked. That was odd, put it into reverse bucked again. Then driving around it was shifting very harshly, trouble "finding" gears, grinding type sounds, nothing pretty. (I never experienced any issues with the transmission in the past. I even got the transmission fluid changed by the dealer a few months back and it was smooth as ever.)

Dejected, I called the mechanic back and they said to drive it around for a few days to see if it would go away on its own, as they really went to town hosing off any spilt gasoline and could have gotten something wet. Sure enough after a few days of sitting outside in 80+ deg sunny weather and driving around it seemed to smooth out but never back to normal before all this. No more bucking when putting into drive but still a little hesitation in upshifting and downshifting. I took it up to 50+ mph but not on highway.

Did anyone else experience similar issues with their transmission after an engine bay / undercarriage wash? I'm afraid to take it on the highway but is that something I should try? Would I cause any damage to the trans if I keep driving it? What outside of the transmission could cause this problem?

The mechanic that did the sensor agree to look at it again this week. But in the meantime I want to arm myself with some knowledge.