I have an Ultra Hub H500-T and recently have been having issues with the 5Ghz wifi network. After a few hours no devices can connect to the 5Ghz network, they all give authentication errors. Restart the router and they can all re-connect however this only lasts for a few hours before I need to restart again - not ideal.
Factory reset the router,
Changed WiFi Channel.
None of the above have made any change, all of my devices cannot connect to the 5Ghz network after a period of time. This router is only 4 months old, but I am leaning more towards a hardware issue with the router.