Update 2:
Problem finally solved! I never ever had such a strange issue as this. One of the Silverstone PSU cable have only 3 molex connectors on it and I was using 2 of them to power drives (HBA ones) through a two pieces of molex-> 2 x SATA adapters. I used third molex connector to connect old Zalman 120 mm fan to cool HBA which only have a molex connector. It turns out that this Zalman fan and Ironwolf drives do not like each other and when they are connected to this practicular Silverstone PSU via one cable fan is causing some kind of interference manifested by random logical errors in ZFS file system which is leading to disk randomly showing up as faulty or unavailable. As soon as I disconnected fan all problems just gone and everyting is working like a charm. What is even stranger – when I was searching for reason of problems I disconnected all Ironwolfs from HBA and connected my spare WD Red 1TB drives to infected system and it did work without problems.
I’m suprised that Silverstone PSU didn’t filtered interferences. One thing is sure, this Zalman fan is going to junk, I should buy new fan instead of doing recycling. Lesson learned.