@Jetman44,

I would have expected a complete factory reset to fix anything like this. Do you have anything unique about your network configuration, such as connected APs or Range Extenders? I would recommend removing any devices that may be extending your wireless network to see if they are the cause of being unable to change the password?

While I am not looking for specifics, you may try to either shorten your password, or choose a password that only has alpha-numeric characters, as extensive passwords can sometimes cause devices to not connect to the network.

After resetting, try deleting the SSID from the list of saved networks. Your devices may be using an older certificate from a previous reset, which would cause the reconnect to fail as soon as the lease were to expire and it needs to refresh.

Also, after resetting, is the password just returning to the default username/password when you try to change it? 

Try setting up your guest network to see if the behavior follows, if there is no issue, there may be a setting causing these issue.