Actually, these problems are regularly described here in hundreds of posts: through UPNP / DLNA you cannot normally control the volume of the renders. As can be seen, the developers do not go into the essence of the problem and it has been there for years.
MacOS 10.14.7, Mac Pro, Audirvana Studio (last), MinimServer, Technics SL-G700, UPNP. When I try to use the volume slider, it “pops out” from under the cursor and goes to 100% on its own. I thought I was going to lose my speakers.
There is no such thing with any other application. Not even a trial period helped. The app has been uninstalled. Too bad.
This kind of problem exist from a lot of time, and not only this, also that the track jump sometimes after one hour of use.
I think that the problem is about some timeout application or the upnp controller.
I hope that the developers fix this kind of problems.
I experienced the same problems ( the volume pops out when using the cusor, track jump sometimes after one hour of use) since the launch of AS.
Curently : MacOS 11.6, AS 1.7.2, Devialet Phantom with UPnP.
Video with described issue. Again same - https://youtu.be/vfpftvPgXq4
All this kind of problems, jum track, volume and so on, take place after one hour of use.
The problem could be, cache, timeout for some function, i don’t know, but if you use it for half day you must reopen all apps.
for me the volume problem appears immediately ( as soon as I want to change the volume with the cursor with the first track I play) !