If you are experiencing Wi-Fi issues, it is important to make sure the 2.4 Ghz network does not have any interference, and it is a distinct network compared to a mixed 2.4Ghz/5Ghz network.
Please check this wiki article for more information: Wi-Fi / Network connection guide for X1/X1C 3D printers
There is a dedicated page for the firmware download for X1 and X1E