I’m frustrated

DM5 - hi-hat problem - ocasionally plays closed instead of openned

Hi all!
Recently I have become a fortunate owner of DM5 alesis drumkit. I liked playing on it very much, but one thing makes me angry with drumset.
This thing is that my hi-hat during playing as openned sometimes (let's say 1 of 15 hits) triggers as a closed HH. Completly have no idea why.
When Footswitch is pressed, HH plays properly as closed, inproper sound as openned doesn't happen. Error only happens during playing openned HH - ocasionaly it changes (for one hit) to closed and it is very annoying. What i have checked already is:
-Error happens while playing very quckly and very slowly
-Footswitch is fine - I plugged it off and this error also happened
-Jack cable is also fine, I switched it to other trigger and cable was fine.

What can be the reason, how can I resolve it?
Any tips are welcome.

PS Happy new year everyone.
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