So I will share a little update to this thread so anyone who has the same problem (and is not a synth tech) can take advantage of this ( I hate to read forums when people describe a problem but when they find a solution they don't bother to post it making the thread useless to anyone in the future).
So I have noticed, that the problem was not the filter but the amp level. When I have lowered the VCA envelope level on the front panel by half, the 3rd and the 5th cards were silent with the light velocity touch on the key.
There was also a trap. I have taught, that the initial VCA env. level on the voice card must be adjusted. It was not that.
The solution of the problem was actually the initial touch level on the TRG1 card. I have discovered, that it is critical for any percussive preset like Electric Piano or Guitar. I hope that it will help someone.