There are a couple of threads that offer help in this area (I suffered this in the beta for 1.8 as well).
There is some advice in these that can be useful in trying to debug this problem.
As far as I am aware, a fully working fix was never offered by Roon
Roon Core Machine
QNAP NAS TS-473
Networking Gear & Setup Details
SYNOLOGY RT 2600ac
Connected Audio Devices
Sonos S2 devices being the issue
Other devices connected : BW Formation Duo, BS Powernode 2i, Lumin U1Mini
Number of Tracks in Library
Description of Issue
My Sonos devices are disappearing from Roon @dylan . I understood you know the issue from beta testing. I am talking about Sonos Streaming devices, Airplay Sonos devices are still there. Please refer to :
https://com…
+1 on this issue.
Started after latest 1.8 update yesterday.
Have 3 Sonos devices: 2 x Play 1 and 1 x Play 5.
All connected via WiFi.
The 2 x Play 1 keep disappearing from both Roon zone picker and Audio setup tab.
Only way to bring them back is to reboot my ROCK.
They are then available until randomly disappearing again.
This has happened 4 times since updating 1.8 less than 24 hours ago.