I’ve been using Roon for quiet some time and it’s been very consistent and stable. I I use Mac Mini 2018 as a Roon core and a Bricasti M3 with network renderer as a Roon end-point. There’s no variation in sound quality. What you’re describing sounds like a compatibility issue and or network problems. I’m not familiar with your components but I would post on Roon forum if I were you, in a tech support section, and attempt to get some help and figure it out.
As a test, can you use USB cable between your streamer and DAC? If so, try it and see if the issues still persist.
About ready to give up on Roon and my streamer
Last December I started a thread to address the question of whether a true AES/EBU cable would sound better than a standard XLR when connecting my Sonnet Morpheus DAC to a Sonnet Hermes streamer. As the discussion evolved, (and in the end I abandoned both connections in favor of I2S via ethernet cable) I began sharing my trials and tribulations setting up Roon and getting it to work. Though I was finally successful and did get to spend some quality time streaming favorite music through Qobuz on the Roon platform, I've never been entirely happy with the sound. Apart from the headaches of getting everything to connect together every time I turn it on, I've also experienced some bizarre intermittent sound quality issues with Roon that I'm becoming very frustrated with. Sometimes it sounds pretty good, and sometimes it sounds tinny, shrill, and no stereo image. I haven't changed any settings anywhere, but something's clearly not getting processed correctly. At this point I'm tired of fighting with it.
What I'd really like to do is take Roon out of the equation entirely and connect directly to Qobuz through a streamer, but the Sonnet Hermes is designed to be a Roon endpoint and as far as I can tell, nothing more. If there's a way to get it to connect directly to Qobuz, I'd surely like to know about it.
Meanwhile, I'm happy to take suggestions for a streamer in the $1K to 1.5K range (new or used, happy with either) that can do this. I really don't want anything with a built-in DAC, as I'm really happy with mine, despite some minor shortcomings in its array of input connections.
Advice greatly appreciated. Thanks!