Just to post my findings regarding this problem. I’ve updated both, Z-Stick S2 firmware (to v3.08, not sure what version it had before upgrade) and Z-Stick S2 Windows driver (to CP210x driver from June 2019; previous driver was from April 2018). After that, I’ve upgraded OH to latest snapshot, but Z-Wave devices (I guess controller is problem that causes other devices to misbehave too) are still changing state from online to offline and vice verse every minute or so. I’ve reverted to backup and I will leave it that way for some time, to see if some future OH update will solve this.
Best regards,
Davor