Manually configured data rates 5.4?

Can anyone explain to me how to manually configure data rates in 5.X? Every time I try to manually configure data rates on an AP running 5.x the clients disconnect and won’t reconnect until I set the data rates back to default. I have tried about everything to get it to work, not that there is that much to setting data rates to begin with.

Thanks,
Chadd

I am having the same issue and have test both 5.5 and 5.9 whenever I set datarates or set ack value on access point to anything other than dynamic clients drop.

Access point and clients are mikrotik running sr9 radio cards.