Changed the subject because I don't understand nobody is even giving an reply to this weird behaviour....

Original text:

In AP conn rates are configured to 12 and 24Mbps only (10Mhz bandwith in 5Ghz band)
Connected client has rates set to default

Strange thing is that when opening the registred client in AP-winbox and look in the client window for the signal it shows a signal strength for 54Mbps as well!

Why?

Even if I set client to manual rates and disable the 54Mbps it is still showing that rate in the AP.
It is even more weird that the 54Mbps is not shown in same window where signal from the AP can be seen in this client.

Any ideas?

Nobody seen or finds this weird?