Like the last macOS-Versions before, if i set up Airplay on iTunes...
My iMac cut my Ethernet-Connection, (i noticed this if i copy Files to or from my NAS. That interrupted and stops.)
Sometimes i see an orange Symbol on the right upper Side on my iTunes-Window, really short to see...
I have to reopen iTunes without any Airplay, select the Airplay Clients and restart the Playback.. Sometimes it works, sometimes not.
After this,(if it works) i can restart the Copying again.