I am running Roon 1.8 (build 764) on a MacMini M1 with Big Sur over wifi via Google Mesh setup.
Since the latest update, I have to try at least 3 or 4 times before Roon will cast to my audio devices. This happens both with NVIDIA Shield when trying to connect directly from my primary computer but also when I use the Roon remote on my iPad to connect with my Google Nest wifi speaker. This is a new bug that did not happen previously.
The first two times there is no response but on the third try I get an error saying the audio device refuses the connection. Then I have to wait and usually when I try again after that message I can establish a connection.