darkstar

My 2012 rubi, w/auto trans will on occasion, when accelerating, will downshift hard/bump/stumble on the shift. It does not do to any routine that I can associate with it. I did change the fluid, filter and inspect what I could see and saw nothing out of the norm. (nothing fell out and the magnet was not heavily covered. I did just come off a road trip doing the TransAmericaTrail(TAT), 8500 miles of some rugged dirt road, dusty and rocky terrain, but my armor protects the undercarriage well.
I find some info during research that says to check or replace the crankcase position sensor, transmission speed sensor, idle air control (clean), pedal sensor assembly. I am old but can do what is necessary and I just do want to be a parts replacer. I did power wash the engine.and it seems all was well until I did that. Cannot be sure.
If anyone can offer any help this old Vet will greatly appreciate it.
Thanks in advance!

Haynie79