Sudden Ubuntu 20.04 Network VLAN Weirdness

OK, doing a bit of maintenance on my two Ubuntu VM hosts in my lab today (apt upgrade on both) and all of a sudden the networking in my virtual machines has completely broken on one host but not the other. Both running the same OS, both identically configured and both connected to switch ports that are configured the same. Notably, both machines worked fine this morning.

Both hosts have basically identical netplan configs as below;

network:
  version: 2
  renderer: networkd
  bridges:
    xenbr0:
      addresses:
        - 10.10.10.217/24
      gateway4: 10.10.10.254
      nameservers:
        search: [<private>]
        addresses: [<private>]
      interfaces: [enp182s0f0]
    bridge102:
      dhcp4: no
      interfaces: [vlan102]
    bridge101:
      dhcp4: no
      interfaces: [vlan101]
    bridge99:
      dhcp4: no
      interfaces: [vlan99]
    bridge2:
      dhcp4: no
      interfaces: [vlan2]
    bridge1:
      dhcp4: no
      interfaces: [vlan1]
  ethernets:
    enp182s0f0:
      dhcp4: no
      mtu: 9000
    enp182s0f1:
      dhcp4: no
      mtu: 9000
  vlans:
    vlan102:
      accept-ra: no
      id: 102
      link: enp182s0f1
    vlan101:
      accept-ra: no
      id: 101
      link: enp182s0f1
    vlan99:
      accept-ra: no
      id: 99
      link: enp182s0f1
    vlan2:
      accept-ra: no
      id: 2
      link: enp182s0f1
    vlan1:
      accept-ra: no
      id: 1
      link: enp182s0f1

The config is mostly so that the first interface can go to storage (NFS over 10G) and the other NIC is dedicated for the VM's. Notable that the same identical config with a different IP works fine on the other host.

Also notable, I can use "ip addr" to assign an IP to any of the bridge or VLAN interfaces and it works just fine, I can ping it from other hosts and so on so I know my VLANs aren't broken. What's broken is specifically my VM's.

I also noted that when I tried to migrate guests over to my other host, a function that has also worked great up to now I was getting errors that it couldn't access the storage on the destination host... but I confirmed absolutely that the storage existed on both hosts and was accessible.

At the moment I've got my critical VM's for my lab work running on a single host which isn't ideal (there's not enough memory to handle the entire lab). Short of rebuilding my host, I am not sure what to do next in fixing this thing.

Any thoughts before I just blow the host away and start from scratch?