Sorry you’re are having the trouble … my 861v6 drops of the net now again but I find a reboot of it (and sometimes the router) fixes the issue.
Not defending Roon, but the problem with the 218, and the ID40/ID41 800 cards, are that they uses the Sooloos protocol not RAAT. The Sooloos protocol is not as well developed as RAAT and as Meridian no longer support it, any improvement / bug fixing by Meridian is doubtful.
Personal I’d bite the bullet and switch to an alternative streamer that is Roon Ready which does support RAAT. If you wish stick with the Meridian brand then it’s just the Meridian 210 (maybe you could borrow one to trial it) outside of Meridian there are of course other RAAT endpoint options.
There is … Roon Setting → About and then click the cog wheel to configure each device …
As you should see, I have mine set to “Ask Before Downloading any updates” this way I control the timing of the process … to mitigate against update issues.
I also have a “spare” Roon Server installed on another machine just in case, so I can revert back a version if need.
I can’t solve the issue, but I hope this background helps your understanding and options.