ace310, go and pick up 4.1.5 from github
Release 4.1.5 · Zomboided/service.vpn.manager · GitHub
Install that directly over what you have and switch on debug (settings/debug)
You'll need to set up VPN cycling if you've not done that already. This can be done in settings/utilities and you can assign a remote button or key to swap between VPNs.
Set up a couple of different VPNs so that you have something to cycle against. Each time you cycle it'll cause the disconnect/reconnect to happen as if your connection was glitching.
Play some local media or PVR or whatever the selection of media is that you consider to be local and cycle the connections.
In the log, you'll see this line, this example is a steam from an addon :
13:02:21.376 T:8872 NONE: VPN Mgr Debug: Changing VPN. Current playing http//http://sniidevices.scrippsnetworks.com/0232/0232648_6.mp4[/media]
You can search on the term in bold. I've had to remove a : after http: to stop the forum trying to format it as media, you may need to do this too, but please let me know what you've changed.
For each of the different kinds of local media you use, get me this line and a comment on what it is (e.g. local stored file, file stored on an SMB share, PVR stream on local network, etc).
Then play some media that's not local and post up that.
This won't fix your problem but it might help me understand what the different sorts of local media are and if I can filter them out somehow.