In the process of resolving the issue they recommended the bridge configuration and reconfigured the firewall for me.
I find it quite hard to believe that the bridge was recommended. Maybe fixed so it worked, but not recommended.
On what interface did you make the VLANs?
I do not find it hard to believe that it's that bridge getting in the way somehow. I would get rid of it. This is much easier-done from an interface that is NOT a member of the bridge as it is trivial to lock yourself out playing around with Layer 2 there.
I would:
In the Web GUI got to Interfaces > (assign), Bridges
Edit the bridge. Remove the interface corresponding to igb3 from the bridge.
Edit the igb4 interface, Enable it, set an IP address in some throwaway IP network.
Add a pass any any firewall rule there
Statically configure your management laptop on the same network and directly-connect it to igb4. Log into the web gui there.
Patch the LAN into igb2 instead
Go to Interfaces > (assign), Bridges
Edit the bridge. Remove the interface corresponding to igb1 from the bridge.
Go to Interfaces > (assign)
Change the assignment for LAN from BRIDGE0 to igb0.
Patch LAN from igb2 back to igb0. You should now be off the bridge interface. Connect back to your LAN switch and you should get DHCP, etc if configured and log into the web gui there.
Go to Interfaces > (assign), Bridges and delete the bridge and bid it a hearty good riddance.
Lots of possibilities for lockout and downtime so you probably want to do this in a maintenance window. One of several reasons bridging router interfaces like that is undesirable.