Strange pbr behavior with VMs - Mullvad VPN included

[murmelbahn]

Hi all,
I'm using Mullvad VPN like descriped here:

https://forum.opnsense.org/index.php?topic=15105.0

I have a few VM's, Windows and Debian. I can assign default gateways in the firewall rules.  It seems like they are using it to a half. When I ran apt update they didn't get any files from the servers but each time it is another server. Other Services like SABNZBD on the same maschine are working fine. Sometimes I get a timeout, sometimes websites are loading. Continuously pings are working. Sometimes the ping doenst get "through" at the first try but when i try it again its running. I really don't know where to look at. Can someone give me a hint?
Thanks!