Thanks for the answer , Christopher
The survey on this client was done a few years ago based on the AP7632, we recently replaced these APs for the 310. We are experiencing these issues only in Macbooks, connected to the 310, we have connected some 7632 in some rooms, and these devices have a stable connection again (Even in 40 or 80 Mhz).
To be clear, other notebooks like Dell or Lenovo have a stable connection, even connected to the AP310, only Macbooks go through this instability.