Controller not detecting APs

[Flying_IT_Guy]

My company has a MSM 720 (running 6.6.5.0) and everything worked great until somewhat recently. Since an undetermined time ago whenever the APs lose power or are uplugged for maintenace, they are undetectable to the controller until they're factory reset at which point they immediatly show up and can be readopted into the system. We're not sure when exactly the issue started as we rarely power cycle our switches and they're all protected by UPS units and a generator system behind that, so power downs are rare. My initial thoughts were this could be related to when we upgraded our fw last summer (as is somewhat typical we missed a few updates and then jumped ourselves up to current). I've seen a few posts with similar results that were fixed by renaming the APs to names without spaces, but that didn't resolve the issue. Any ideas would be helpful, it's not a critical issue it's just a pain to haul out a ladder and pull APs off the ceiling (a few in very difficult spots) to factory them.