Hi, I've faced the same issue, just now.
I run couple psSense 2.4.4-RELEASE as a virtual machine on a XenServer 7.2.0 HA cluster without any issues about 2 years.
Before now, I used dedicated virtual network interfaces to connect virtualized pfSense VMs to my VLANs. Couple days ago I decided that its time to connect pfSence to a trunk and configure VLANs on it.
I did it and it works but with MTU issues. It looks like it works but at the same time, heavy traffic like SMTP over TLS doesn't go through or heavy https web pages can't be opened. 1469 is the largest ICPM packet size can go through the VLAN interface.
So, I would appreciate if anyone can help to resolve the issue and a specially if the topic starter can share his experience and explain what was wrong with the kernel drivers for the server NICs.