Aha! It seems that I can reliably reproduce this. For me the steps are:
1) Plug in an external mouse
2) Move the external mouse
3) The start of the first set of scroll events from the touchpad is bad (scrolling in the opposite direction). After the initial bad events, scrolling works as normally until I move the external mouse again.
Aha! It seems that I can reliably reproduce this. For me the steps are:
1) Plug in an external mouse
2) Move the external mouse
3) The start of the first set of scroll events from the touchpad is bad (scrolling in the opposite direction). After the initial bad events, scrolling works as normally until I move the external mouse again.