Guys, thank you for all the help!
Charlie you got it! In your last sentence, that what was happening:

"At the moment, my guess is that because of the short duration of the drum hits, the Mute function may not be catching the first 'hit'..."

It sounded well, not as clipped note, but as somebody stepped on the frog.

I exported whole drum line and everything is fine, those "bad" notes are playing as they should. It will only take me a few minutes to work the mutes in DAW. I guess it is not very common.

Again, thank you!

Mike.