I had similar problem in the 'SSID availability', there were several old tags for access points that no longer existed.
Long story short, there were a few SSIDs that we had originally set to only be available on a few access points, which we later changed to 'enabled on all access points', but DID NOT remove the tags from the 'enabled on some access points' before making the change. The old tags were still listed if we looked back into the 'enabled on some access points'. I deleted the tags from there, then switched back to 'enabled on all access points'. The dead tags disappeared.