WAX206 Dropping Wireless Connections

I installed a new WAX206 router in June for my church, with the following configuration: business high-speed Internet modem/gateway, connected with coax cable to business Ethernet/Wireless router (owned by ISP), connected with Cat6 Ethernet cable to Netgear WAX206 router (to manage internal network). Wired Ethernet network is routed from WAX206 to a Netgear GS724Tv4 smart switch; wireless network is controlled by WAX206. Wireless 1 settings have 2.4Mhz disabled and 5.0Mhz using WPA2 security for the primary internal WiFi network. Wireless 2 settings have 2.4Mhz disabled and 5.0Mhz is an open WiFi for public access. Wireless 3 is disabled. There are separate SSIDs for Wireless 1 and 2. There is a Netgear EX1500 network extender located about 30 feet from the WAX206; to provide broader WiFi service to the offices in the building.

For the past few weeks, the WiFi signal has dropped off for several minutes at a time (sometimes up to 30 minutes) without any indication of a problem. Aside from rebooting the WAX206 device, is there something else that can be done to ensure we don't keep dropping the WiFi service/connections?