Hi,
i have a problem with one AP what we have in area with about 40 people. There is RB600 with four R52N(R52 before) cards and 17dB sector antenas...client has RB411 with R52(22dB parab. antenna) I discovered it not long ago...before it was everything OK.

example: client is cca 500m far from AP, signal between client and access point is about 65 on both sides...CCQ is 90/90. when I run bandwidthtest to client from AP 8Mbit FD...CCQ fell down to 60/20. we using free frequeces in this area and also neer frequenses are free.
...and client's neighbour 100m far away (same direction) have CCQ 80/80 10Mbit FD traffic- everything OK

For sure we tried change frequency,antenas, coax cables, cards...simply all

It's same ROS version/equipment on both clients ?

We have same problem, Mikrotik, 5G, omni antenna and ~10 clients connected. Clients that have NanoStation 5 works fine with good ccq in both sides (with or w/out active traffic). Others, that have MT have very poor and unstable ccq and rx rate, in same time, tx rate and ccq is very good on ALL clients (UBNT and MT).
Also tried to change freq but same result. BW test shows about 10:1 difference in tx and rx troughput... ?!
On AP side is 3.23 (x86) and clients have from 3.20 to 3.30 i think.

I think that problem is in version of ROS. In my case, it's not same on AP and on clients side.

MT support ?