Hi. I have been experiencing what has been called the "bump/jerk" on GMC hybrid trucks. The symptoms include a jerking sensation as the vehicle switches between hybrid mode and engine mode. This can also cause pauses in acceleration or also sudden accelerations at low speeds. This is typically accompanied by OBD-II codes P2797 (Auxiliary Transmission Fluid Pump Performance) and/or P0C2B (Auxilliary Transmission Fluid Pump Control Module Feedback Signal) and/or P0AC4 (Hybrid Powertrain Control Module Requested MIL). This may also cause other systems to illuminate the Check Engine light - in my case, there was an Emissions System Not Ready OBD-II error.
There was an unofficial bulletin floating around but I came across a PIP (preliminary information post) from GM and the NHTSA. This bulletin specifies the first resolution for this issue is to replace the auxiliary transmission fluid pump control module (GM Part Number 24261817) and a couple of harnesses (24259589 and 24259590). There were some early reports that the control module was only available from a GM service center but it seems these are now available online as well. Parts & Labor this was a $637 fix and it seems to be working. Not sure how easy this replacement is for you DIYers.
If the control module is *not* this fix, then the next step is to replace the auxiliary transmission itself, which is about a $1200 fix.
The GM bulletin can be found at https://static.nhtsa.gov/odi/tsbs/2018/MC-1015