Thanks for the info. Please check if you are able to move the playhead position properly using the mouse. This will help us in isolating if the issue is occurring specifically when using Wacom Intuos as a controller. If its specific to Wacom Intuos, then please try to update/clean install the latest drivers and check if it is helping.
I'm using intuos 4 with 6.3.40-2 in PremPro 2020 on latest Catalina. I'm using the playhead position to scroll forward and mark an out point but the playhead bounces to the end of the clip. There's no controlling it.