Hi Marcos,
So are you saying that the AP disapears from the controller for a little while, then comes back?
Are the APs in the same subnet as the management/ AP manager interfaces? I would do a debug lwapp events enable and check how many broadcast sources you have in this subnet. It happens that when there are too many sources of broadcast, APs get disconnected; isolating the APs in another subnet/VLAN usually solves the issue.
Tx
Jerome