I had been convinced that upgrading HW (and a new contract, haha) will help to resolve such problems. But in reality, it was not working perfectly from Day 0.
From time to time I can observe connection drop and quick recovery. It could be 2-3 cases in a row, during one-two hour. The stable work for a few hours. and again. If I am "lucky", I can have such a sequence only once during working time and repeated only in the evening.
Funny thing is that the new HW doesn't log everything, but only the last cases with reconnection. So, if I had 5 drops in a row, only the last would be logged. Looks like "only one drop", but it WAS NOT.
So, now, I download the log file after each drop, just to prove that the connection is not stable and that the problem is NOT on my side.