In my experience the problem is in the router, not the device. The router tries to push traffic to the faster SSID forcing a disconnect on the 2.4GHz device and expects it to reconnect on 5GHz but of course it cannot. Somehow this process seems to leave the device in a bad state.
One solution is to change the SSIDs of the two networks so the router cannot try this trick.
Another solution is to find the setting in your router and disable this feature.