Many "just works" things on the local network start failing for me when I'm using a VPN. Maybe check whether that's the reason. But yes, generally the reliability is so-so. Also, the feature to use Apple Watch to unlock the Mac or iPhone works mostly, at best.
I don’t use a VPN and I don’t think it’s my network because I don’t have any problems with “old” protocols (UPNP, samba, RDP/VNC, SSH, everything on top of HTTP). I wonder what Apple’s protocols do that makes them so error prone. If it was one or two of those I’d say it’s a bad department but the amount of errors suggests a deeper problem in the way Apple develops these things.
