What I am looking to achieve is the ability for my openwrt device to receive a VLAN tagged packet and foward that packet with a different VLAN ID.
For example:
port lan0 is a tagged port for VLAN ID 2
port lan1 is bridged with port lan0
the packets tagged with VLAN ID 2 is received at port lan0 and sent out of port lan1 with VLAN ID 20
a.k.a. VLAN translation
Bridge lan0.2 with lan1.20
For some reason this works for my edge router 4 but not for my rb5009.
For my rb5009, bridging devices work but bridging vlans of devices do not.
Really? What shows
brctl show
and, for both interfaces,
ip -d link show dev lan0.2
And maybe compare that with the edgerouter.
As a general note. Please note that such hacks should only be used if you inherent a total bonkers network setup and need to transition to a clean architecture.
What's the initial reason to do that? Why can't you just use one vlan id for those network segments?
I must have made a mistake somewhere but it works now after I re-did the config. 
Apologies for reviving this thread for nothing.
This probably isn’t a normal use case but it is to allow distinguishing of duplicate vlan tagged traffic based on ingress interface.