I think my SSD drive was going mad. For example rebooting is very slow and produces error messages from file system mounting etc. >:(
Also file system check did never get disk to shape, I had to run it every startup.
I have seen strange behavior after power failure few days ago (even I have UPS), so maybe it has affected to ssd disk somehow.
Luckily I have recent disk image backup, so I restored it and everything works now. I have to wait if this strange behavior continues, and then try to replace disk.