Q: Jerking and high rpms

Aright so we bought this truck second hand on the 31st of October and the previous owner said it just needed a left strut but that's not the problem the truck did not have issues until early April but here's the the thing the truck would be in first then would jerk forward when up shifting or downshifting and would jerk very violently like if you just got rear ended going like 40kmh and the rpms will shoot way up like it's trying to shift but won't I noticed that it won't like catch gears the Mechanic first said his scanner showed up saying it was 2 solenoids but he checked them all and said they were fine so he said it was probably the computer in the truck (ECU) so we paid about $1200 for the part he put it in and said the problem was fixed because he test drove it and said there were no problems the jerking and stuff stopped so I went to pick it up but sure enough it started doing it again but worse now he said it's the transmission sensors and solenoids what do you think it is?