Issue:
If you have a MikroTik router configured to use multiple VLAN's and have connected to a Ubiquiti US Series switch you may find traffic will not pass to the MikroTik if the VLAN tags are assigned to an Bridge Interface used as an uplink trunk and other Bridge Interfaces have Ethernet, Wireless & the VLAN Interfaces assigned.
Remove (or disable) the VLAN's and traffic flows through the port OK (although the routing fails due to no VLAN tags).
Solution:
The issue is the Spanning Tree Settings within the Bridges.
If Spanning Tree is configured for RSTP within the Bridge Interface you MUST change it to NONE or STP as below
This will now allow your tagged VLAN traffic to pass onto the MikroTik where you can route it as required.