DIAGNOSIS This is typically caused by interference from neighboring Wi-Fi networks or incompatible device band steering. The system's algorithm is aggressively moving devices to 2.4GHz due to perceived instability on 5GHz.
FIX Manually disable band steering. In the Google Home app, go to Wi-Fi > Settings (gear icon) > Advanced networking > Band steering. Toggle it off. This forces the router to broadcast separate 2.4GHz and 5GHz SSIDs. Connect your devices directly to the network ending in "_5G".
IF THAT DIDN'T WORK The issue may be specific DFS channel interference. In the same Advanced networking menu, tap "WPA3". Toggle it off. WPA3 implementation can be unstable with some older 5GHz clients, causing disconnections.
HEADS UP Turning off band steering means you must manually manage which band each device uses. Some IoT devices will only connect to the 2.4GHz network.