From a Windows command line one could use dns-sd -B _googlecast._tcp to browse for announced GoogleCast services (hit control + c to stop browsing). Is there anything unusual/unexpected in the listed announcements? Do they change over time?
Note: Maybe this issue is network related (devices hopping WiFi networks {2.4 – 5.0) or access points or access points hopping channels), leading to multiple concurrent or duplicate entries over time for the same device? I also use different ChromeCast devices in my network but don’t get this duplicate entries. So it seems the technology can work as expected and the question is what goes wrong in some other users environment.