does someone have some news about that very strange problem ?
I have downgraded to RouterOS 2.9.3 and did a /system reset.
All seems to be ok now. I'll make others tests (upgrade and see the difference with the same antenna, same cables, same CPE).
I'm facing the same issue from 1 month. But I have used for the first time RB, before I have used RouterOs as server in a PC based, never for wireless.
Using CM9 as using NMP5354.
What I have seen in both the boards is that the behavior is better from channel 1 to 6 while from channel 7 to 11 the communication between clients and AP is worst.
Periodically I cannot get ping response from the clients for about 2 or 3 minutes.
The signal form the registration table for a particular client near to the AP is about -55 and SNR is 42db, while the worst client is about -70 with SNR of 22db.
The clients are not disconnected by wireless, but seems that there is no route between the AP and the clients . I have using simple bridge between wireless and WanEthernet.
If your trials are positive, try to use the NMP5354 (if you have one) becouse this is last Atheros chipset, and I have dubt about the older drivers.