Comment 8 for bug 1210575

Till, could you please run
xev | tee taps.txt
and tap like 5 times right in the middle of that xev window. Try to perform the taps like you always do them when trying to use Onboard's right click.
Attach taps.txt here, maybe there's a clue in there.

I'm currently working on a replacement for the middle and right click conversion (for bug #1191098) that would probably sidestep your problem too. It has yet to be tested on touch-screens, though...