Two different issues, completely unrelated.
In most previous instances of the volume issue, it’s been a controller with a stuck button that’s been the causes the volume adjustment. Check for various mobile controllers that might be in jeans, or with stick buttons, or even remote controls under the couch cushions, so to speak.
Audio cutting in and out has been extensively and frequently covered. In most cases, it’s an issue with wifi interference of some type, I’d encourage reading the linked FAQ and applying such solutions as might fit your particular situation, since there are a raft of different situations depending on your setup.
However, if neither of those suggestions work, you can always submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.