Couple of thoughts.
First, try a simple network refresh, by unplugging all Sonos devices from power. When they’re all powered down, reboot your router. Once the router comes back up, plug back in the Sonos devices,
Second, in general, Sonos isn’t always happy with mesh networks, as the Sonos devices talk to each other so that they can stay in sync. Many mesh networks tend to block that inter-speaker communication for a variety of reasons, which makes the Sonos system a bit challenging. I usually recommend a wired Sonos system in order to obviate those potential issues. The key to a wired system is the one device that you wire should be wired directly to the ‘root’ or ‘hub’ of your network, and not one of the satellites. You may want to try plugging a Sonos speaker or BOOST directly to your hub Velop device, and see if that clears up your issues. You’d need, of course, to be careful that the Sonos network is on a different and non-conflicting channel as your Velop of course.
There’s some good information in the wired and wireless modes FAQ.