We've some strange performance effects. We see tcp degradation to some (not all) targets behind a ccr.
We guess it has to do with mixed routing/bridging.

How does a mikrotik virtual bridge work compared to a HW-switch?
Esp. does it buffer all packets or does it drop packets if a limited buffer space is used?
Is it simple FIFO or does some packet reordering happen?

Do you see packet loss and/or latency increase through the path when it is under test?

Do you see packet loss and/or latency increase through the path when it is under test?

We see decreased tcp-performance for traffic running this path.

what kind of queue associated to the port itself?
if it's hardware queue, try to switch to pfifo with ~500packets