I've got a weird issue going on and can't figure out what's causing it.

Keyboard is a Logitech UltraX Premium USB

Symptoms:
In ETQW whenever I keep pressing a modifier key, as soon as I press any other key the modifier "unpresses".
It's not happening in QL and in Windows itself.

What I have tried is using a friend's keyboard, which is an HP KB-0630 with PS/2 and I'm having the same issue. USB is plugged in different ports (USB2 and USB3, front and back).

When I connect my UltraX to my laptop, the issue isn't there, so I suspect it's a system thing.
I have disabled all the sticky/filter key stuff a long time ago.


Anyone an idea what it could be?