Hi, I have been experiencing a similar but more critical problem recently. Roon recognises my Meridian 818v3 and MS 200 when you power them on and then drops them after a few minutes at most (or a couple of seconds if I select them as a zone to play). They only reappear if powered off and on again with the same effect but basically cannot be used for playback directly any more.
Roon server runs on an i7 windows PC (Quiet PC i7 8700 running Windows 10 Home) with the following set up:
PC (1) => 16 ethernet gigabit TP link switch (2)=> MS 200
PC (1) => 16 ethernet gigabit TP link switch (2)=> 8 ethernet port gigabit TP link switch (3) => 8 ethernet port gigabit TP link switch (4) => 818v3
All linked up by cat 7 cable between the switches.
My router is a Netgear Orbi linked to switch (3). Up to a year ago it was set up in lieu of switch (3) but I then also had problems and having read on these forums that putting a switch between the router and the rest of my home network may solve the problem, I tried that and it has worked until now. IGMP proxying is disabled on the Orbi. (the Orbi is only linked to switch 3 and the internet). The Orbi does detect and list both the MS 200 and 818v3 in the list of attached devices and assigns them an IP address. I use a Global Cache iTach to run vMSR to control the 818v3 through my iPad which works fine. I can also access both devices through their web pages when entering their IP addresses on a browse.
Connected to switch 4 are also a Lumin U1 mini which feeds into the 818v3’s USB (for direct DSD playback) and has no issues working with Roon and into the 818v3.
A Bluesound Pulse is also linked by cat 7 to switch 4 and has no problems with Roon.
Other devices are connected wirelessly (Bluesound Pulse mini, all Chromecast, iOs or Android devices) are also recognised and play back with no issues from the main Orbi router or either of the 2 sateliites.
I did try to play around with the Orbi settings thinking that might be the problem but nothing has helped and it seems others have a problem with disappearing Meridian devices.
All switches are basic unmanaged switches.
Bitdefender used as firewall programme (replaced Kaspersky 6 months ago as it was slowing down Roon and demanding to be reauthorized far too often for my liking) but once Roon and its various applications were authorised the first time all has been fine.