Hi Eric - thanks for reaching out. Here is my setup.
Roon Version 1.5 (build 323) stable (64 bit)
Desktop computer interface with iMac OS 10.13.5
Devices affected included several iMacs with remote ROON access, iPads, and iPhones. When core is not available on one device, same is true for all devices
My music is stored remotely on a QNAP NAS TS 451+. The set-up was copied directly from the recommended setup described in the Roon Support pages (i.e. ROON server installed by itself on SSD while my music files are on three 4TB SATA drives in a RAID 1 type setup, I believe.)
As for number of tracks, I don’t know exactly but I have about 2500-3000 CDs ripped to my NAS.
Regarding my Network:
I use an Airport Extreme Router, firmware is current. It is hardwired to a Comcast (cable) Modem which is a dedicated line into my home (i.e. not shared with TV or any other hardware).
My NAS is hardwired to my Airport Extreme.
When ROON cannot find the Core (happening on a daily basis) I cannot locate it on all my ROON remote devices. However, my music files are readily available when I search from them from my desktop computer, so I know that the NAS is online and available wirelessly within my WiFi network. It’s just that the ROON software program cannot locate the ROON server on the SSD drive of my QNAP until I reboot the entire NAS and then ROON easily finds the server and all is good.
I might point out that I’ve been using this setup for at least one year now and I’ve only had this problem sporadically maybe 2 or 3 times in the past year. Now it’s every day and very frustrating as it takes about 10-15 minutes for the NAS to reboot fully and ROON to locate the server.
Please let me know if you need more information. I apologize if my descriptions above are not technically accurate but I’m very much a novice with these things…