RBW30 Crippling Certain Devices

I believe all firmware is the latest release for each device (though I'll repeat that this issue has persisted across a few upgrades now).

RBR20 - 2.5.1.16

RBS20 - 2.6.1.38 (updated within the past couple of days)

RBW30 - 2.6.1.6 (updated last week)

House is ~3400 sqft. Distance is probably between 30-40 feet. The RBS was on ethernet backhaul prior to my recent test. The RBW was reporting good backhaul connection at all locations tested. The devices in question are 15-20 feet line of sight through a window to the RBW30 locaion(s). 

When the RBW30 is removed the devices will connect to other access points, further away and show link rates greater than 1 Mbps, but between 10-15 probably due to distance from say the RBR20.

Armor and circle aren't used. Daisy chain has been on, but the devices never connected in daisy chain mode. Fast roaming and ipv6 have been on. 20/40 coexistance has been disabled (turning coexistence on seems to give a general problem with the ring devices that otherwise work when it's off). I tried the short preamble the other day and had no improvment. I can try some testing with the fast roaming, ipv6, and preamble.

Good question on the removal of the RBS and using the RBW only. I have not tried that configuration, but will give it a go later today and report back.