I think the backup may now be working. I set Roon to backup everyday at 1:00 PM as a test. Based on this screenshot:
So it appears that the backup ran at 1:00 PM and was completed at 1:06:33 PM. If you agree, then I think all is resolved.
To answer your questions about my network, etc., to offer better clarification- I have a Synology NAS (DS 214) where my I store my music library. I am running ROCK (Intel NUC 5CPYH). While both are underpowered, both seem to run well most of the time. My WiFi is a Google mesh router and I also connect via Ethernet for large transfers.
On the NAS- my music library is stored under the “music” folder (\192.168.86.30\music) while my Roon backup is stored under the “A” folder (\192.168.86.30\A).
Standing by for any additional guidance.