I have decided to remove dedicated SSD that Roon had its own database and add 4th HDD into raid and start from scratch.
Roon now is setup on HDD Raid5 and so far I did not experienced issues like skipping music or stopping, although there is one issue I did not mentioned before (it was when Roon was running on SSD and it is now on raid)
when I stop/start Roon service on QNAP via Web GUI it sometimes takes 10 attempts to start Roon. symptoms:
Roon stops normally
When starting service it is normally shows it is starting, but after a while it says: Roon is disabled
repeat step 2 - sometimes 2.3 or even 10 times to start, then all works ok