You know what's weird? I've experienced this behaviour long before the 7.1 update but only if my server shut down unexpectedly. SInce I've aquired UPS there were very few dirty shutdowns, only like 2 or 3 a year, so I didn't bother looking for a fix and just remembered I have to do one extra reboot and I'm fine. But now I wonder if there's a relation with this now prevalent misbehaviour.
Oh yes, and massive thank you to @husqnz and @Naticus, you saved my nerves. I almost bought a Chromebox and turned it into a standalone nginx/pi-hole machine, which would be awesome and I would really enjoy doing it, but have no time for 😅.