With my Sentelic touchpad two finger scrolling and two finger tapping interfere with each other. ie, if you disable one, the other works as expected. I tried to report this against the kernel driver but they said that the kernel doesn't deal with scrolling/tapping.
Please grab mtview from https://github.com/whot/mtview and check if the data that comes from the touchpad looks sane (no weird jumps, etc.)
If so, please record the device data with utouch-evemu and attach both the description and event file here. Try to get as short a recording as possible to reproduce.
mtview looks fine, but for some reason I am now unable to enable double finger tapping, meaning that I cannot recreate the bug.
Created attachment 63530 [details]
Created attachment 63531 [details]
Two finger scrolling
while two finger scrolling
Issue is that scroll doesn't happen until I lift my fingers off the touchpad.
Created attachment 63532 [details]
Two finger tap
Two finger tapping doesn't work either.
After a cold start today the touchpad was playing up again.
I think I've narrowed it down to horizontal and vertical two finger scrolling that are interfering with each other. If I enable both then it's erratic, if I only enable vertical it's ok.
Two finger taping still doesn't work though.
This is possibly an issue with the driver: https://bugzilla.kernel.org/show_bug.cgi?id=43591#c5
on Jun 27, 2016 at 18:27:26.
(provided by the Example extension).