DIAGNOSIS Periodic, brief disconnections are often caused by band steering aggressively moving clients between 2.4GHz and 5GHz, or a conflicting wireless schedule.
FIX Disable Smart Connect (band steering). Log into the router interface. Go to Advanced > Wireless > Wireless Settings. Locate the 'Smart Connect' section. Uncheck the 'Enable Smart Connect' box. This separates the 2.4GHz and 5GHz SSIDs permanently. Reconnect your devices to the 5GHz network exclusively for stability. Next, check for schedules. Go to Advanced > Security > Access Control. Ensure 'Access Control' is disabled unless you have configured it. Go to Advanced > Wireless > Wireless Schedule. Ensure no schedule is enabled that would turn off the radio.
IF THAT DIDN'T WORK The issue may be interference from a nearby device. Common culprits are Bluetooth speakers, baby monitors, or microwave ovens. Temporarily change the 5GHz channel width to 20 MHz (from 80 MHz) in the Wireless Settings. This is less prone to interference. Test for drops.
HEADS UP Smart Connect uses a single SSID for both bands. While convenient, its algorithm for moving devices can be disruptive to real-time applications like VoIP. Manually splitting the networks gives you direct control. Also, ensure your device's wireless power saving mode is disabled, as it can cause micro-disconnects.