rotary button on a buttonbox

For my SimRacing rig I have build a buttonbox  with LED-matrix, en LCD, push buttons and roraty buttons. All is working perfectly except the rotary buttons.

When I check the button function in windows the click function works, but when I turn or touch the buttons it gives a flickering signal, even when I don’t touch the button anymore.

I have change them, thinking it was a malfunctioning rotary, but that didn’t do the trick.

It are EC11 buttons connected to a Arduino Pro Micro.

Anyone experienced the same problem?