Since updating to the 1.1.1 firmware version, devices that try to connect to the 5 and 6Ghz bands are incredibly slow and are refused connection after about 10 minutes. Have done 2 software factory resets and 2 hard factory resets to no avail. Installed the beta firmware for 1.1.1 and issue still continues. 1.0.12 worked flawlessly. 

EDIT: Shortly after this post the 2.4Ghz band also failed. Have had to change back to Asus AC86U, which had Wi-Fi issues prior to getting the BE800 to replace it.