You probably just need to increase your Prepare Using Buffer for MIDI to 500 per post #2.

Deleting the .ini and rising up the MIDI buffer doesn't make any sense...

If it solves your problem then it makes perfect sense.

Do I understand correctly that the only one solution is to disable the drum map?

Not necessarily. What exactly is your problem, what have you done so far to try and resolve it and please list your full computer spec, including interface & driver mode.

Will the drums still play notes after map will be disabled?

Yes. The drum map just overlays the piano roll, remove the map and the notes will still be there.

To eliminate the drum map, you can assign the output of the MIDI track directly to AD2. This will bypass the map, but leave it in the project. To remove the map from the project altogether, choose 'Drum Map Manager' from the MIDI track output, and delete the map.
 
But if you actually bumped the MIDI Prepare Using buffer all the way to 2500 from 250, try 500 as recommended earlier; too high can also be problematic.
 
Did you compose the MIDI for this drum track yourself, or is it from a 3rd party? Are all the parts in a single clip? Is it hard-quantized? What's the project tempo? Sometimes changing the tempo or moving hard-quantized notes a tick or two off the grid will eliminate problems with dropped notes that don't respond to increasing the Prepare Using buffer.

It seems that my problem was caused by the third-party plugin placed on master bus.
Could say - SOLVED :D

Opps, sorry. In the piano roll it was the bass part. Does your advice applies also to it?

Understood, thank you!
It was ozone vintage tape demo trial. Once trial has ended such behavior has occurred

brundlefly
That's a good one for future reference. But odd that it wasn't causing other tracks to drop out as well if it was on the Master bus...?

Pardon me, just rechecked the project. Plugin was placed on Drum master Buss.
Maybe it's related only to my specific PC with my specific plugins set.

fitzj
I had this problem and when I transposed the midi by an Ocatve all was ok.

That would make sense for a Bass part where the synth tuning is transposed to help accommodate shorter controller keyboards and low MIDI notes fall outside the instrument range, but if it were a transposition problem in this case, he'd be hearing the wrong kit pieces play on notes that weren't dropped.
 
It sounds like the unlicensed plugin on the Drum bus was the culprit. Makes more sense now.