how often does it happen?
It is possible that the wireless clients do not transmit any data and that is why the data-rate lowers.

i guess it's related to http://forum.mikrotik.com/viewtopic.php ... lf#p467177
as i am always having the same problem with rts cts

its clearly due the signal run a BT test with 5MB and paste the outpu of the TX/RX and check your alignment and line of sight make sure its straight forward

Hello.
We have the same problem on Mikrotik BaseBox 2.

In different time clients drop RX rate to 1Mbps, and they coudn't get connection to different servers.

What we can do with this problem?