Do you have other SSIDs that continue to work properly? if not try creating one just to see if it stays up or follows the same pattern as the original SSID.
Does the outage occur at the same time each hour? does it occur X number of minutes after the AP is rebooted, then on the same 50min/10 min schedule or is it a random 50 minutes?
if you reboot the AP in the middle of the 50 minute outage, does the outage shift in time to follow the reboot , or is it x number of minutes after the hour every hour?