Agreed it is an extreme measure but one that will cost you nothing but time to try. You can always restore from the backup. Once your DB gets corrupted in some manner there is only one way to fix it…
This will at least rule out a corrupt DB issue. When you start with a new DB, do not enable any music folders either, working just from online sources. That will also rule out a failing music storage HD too if the problem persists.
My take on your issue is that when Roon tries to update the DB with metadata it is accessing Core DB, Network and of course RAM. So issue is either:
Failing SSD
RAM issue (you need to confirm it is still not running out with 8GB and that NUC BIOS detects 8GB)
Corrupt DB - starting over with a new one is the only fix
Network issues - (I have no experience with mesh systems but Roon is picky…)
The first three are hardware and most likely to cause a server restart I guess but the last should not (error message and log entry more likely).
See also: Roon Remote connection failed TP-Link Deco M4
But if it is a network issue, you should be having other issues at other times.
Roon really do need to look at your logs again.