I don’t have experience with the Synology package, so I can’t help with roor-cause analysis, but I would say the following:
Your installation is not stable (in my view). OH2 process can not write new (or update existing) files to the filesystem… that’s critical.
Forget the rules and the items for now.
Try to stabilize the vanilla OH2 installation first and then start adding stuff to it.
Backup your configs (rules, items, etc) and start clean.
