This must be a bridge issue, I don`t see any other explanation.
We have VLANs, and just now, I made a test to be sure not to give you wrong type of help
I set up a new simple queue on VLAN interface, called ABC, Look at the following screenshot from my winbox:
http://jager.on.panonnet.net/!queue.gif
This interface without queue almost never have less than 2Mbit of traffic.
You can see in the middle of the traffic window for this interface how the traffic significaly lowered when I enabled the queue, (and my users was wondering what is going wrong with the Internet
) and raised again after turning the queue off.
I really hope this helps you, at least, we can be sure that Mtik know how to handle simle queues on VLANs.
!Wait, something comes onto my mind.... all my queues have priority 8.
I still did not made any QoS to favorize certain type of traffic. Do you have different queue priorities on you router? Maybe the solution lies there?
Crossing fingers
Jager