@kogan 

Now, for the client who is unable to convert from AP to ER706W, have you tried other devices? Is this only happening to certain devices? Has this worked properly before?
Also, try adjusting the RSSI settings for the AP.Set the EAP650 signal strength to -60 dbm to disconnect the client if their signal strength falls below that threshold.

If the problem persists, please capture the WiFi packet on a MacBook so that we can look into it.

How to Capture the Wireless Packets on MacBook

  @kogan 

Do you enable fast roaming? You previously tested that adjusting the RSSI threshold might let you transition to the ER706W.Also, you should be aware that this has something to do with the device's mechanism. What are your expectations here?With no RSSI threshold set, but switching to the nearest devices when forwarding it?

Do you compare the performance of two distinct versions of the controller?Also, do you test various devices?Will they all have this problem?Can you try to capture the package so we can analyze it?