I have replaced my triple-WAP581 WDS-based network with three 240AC's, one primary root and the other two configured as mesh extenders. This took some time to get working, since at first I missed the part about needing to bring up the 240AC's with a wired connection before re-configuring them as mesh extenders and only then cutting the cord.
Be that as it may, my problem is that bringing up this three-node mesh on any 5GHz channel other then "Automatic" only ends with the mesh nodes blinking permanent red LEDs. I am using 80MHz bandwidth. The mesh comes up fine if I don't touch the channel settings. However, no matter at what stage of the setup that I attempt to modify the 5GHz channel, it breaks the mesh. This applies whether I leave the mesh extenders on Automatic, or set them to the same channel as the primary root.
Any trick to this? I am using the 10.6.1.0 firmware that came with the 240AC's. Incredibly, that is the first firmware version that even allowes a 240AC to be set to act as a mesh extender.