I switched to the Big Sur OS this morning (after Morave 10.4). When reading with Roon, there are some mini-cuts. Nothing very serious, it’s in the order of a millisecond. Do you have any feedback on these little problems? A setting that needs to be fine-tuned somewhere?
Does your iMac have a hard-wired connection to the router or are you connecting using WiFi? If you’re using WiFI, please connect your Core directly to the router - do you still experience this issue?
Is there any change if you reboot the Core?
Does this happen for all endpoints or only some?
It might also be helpful to have a complete description of your setup using this link as a guide.