Network (sometimes) broken via VLAN interface

Using a VLAN (less than 100) interface created via Settings (standard settings, MTU, using DHCP, etc) and trying to connect to a service via TCP, it times out, sometimes. When looking in Wireshark I see a bunch of TCP duplicate ACKs and retransmissions. The handshake looks good. It’s only when accessing a network routed close (2 routers), but websites on the internet seem to work fine. I tried to disable all other interfaces, same issue. But when I changed the switch port to use untagged traffic on the same VLAN, everything works as expected. I am using the Gigabit Ethernet port on my hub, when I try the same thing with a Gigabit Ethernet adapter it seems to work fine. I am stumped that the hub only works sometimes with tagged Ethernet. I tried lowering the MTU on the hub’s interface, same thing. Anyone who has seem anything like this or know why this is?