Trackpad double click

Hello all,

I'm on a DELL XPS13, which have a cypress CyPS/2 trackpad, supposedly supported on linux since 3.9. I do not use the "click" buttons, only "touch-to-click", touching with 2 fingers to emulate the right click.

3 or 4 months ago, the touch-to-click started to behave strangely, sometimes inputting two clicks instead of one. I blamed the hardware at that time.
However, since 1 month or so, everything is back to normal, except for the need, in KDE (dolphin, etc...) only, to do a triple "touch click" instead of a double "touch click", to open anything.
The double touch click work anywhere else (eg, dble-click to select a word in Firefox).
If I double click with the "click" button, it is also fine.

Only the "double touch click" needing three touches.

Does anyone might have any pointers about where to look for ?
My guess is that someone is fiddling with this setting upstream, but I have no idea whether I should look toward openSuse, KDE, or Linux (kernel/driver).
Any idea of a config file I should try to tinker with ?