WAN instability

[giversen]

Hi,
For a couple of month ago I turned from pFsense to OPNsense without any major issues so far, just 1 annoying issue. One of my 3 wan connections fails after it has been stable online for 5-8 days. I either have to reboot the firewall or restart the failing interface if I can get access to the firewall via either the lan interface or one of the other wan interfaces.
The setup is as follows:
hardware: intel core i5 8265u, 6 Intel 211AT NICs, 32Gb Ram, 1TB samsung SATA SSD
OPNsense runs on the bare metal (but I am considering run it as a vm (KVM) when I have the time to do it )
The WAN connection that is failing ca. once a week is getting a dual stack IPv4 and IPv6 via DHCP, but is using VLAN tagging. I use IPSEC and OpenVPN on the failing wan interface. I am unsure what log files I should look into or what I should look for to mitigate this behavior.
All suggestions or ideas are welcome.
/Jørgen