@udntknw,

Depending on the model of iPhone, I know that some have trouble with the fast roaming option that can be found on our routers, causing devices to stick to poor connections, rather than switching to a more powerful network. For clarification, do the backups ALWAYS fail, or only fail sometimes? If sometimes, is there any pattern behind when the backups fail? Such as timing or what node the iPhone is connected to?

Something that may be worth testing, if you can manually trigger the backup, is to disconnect from the Wi-Fi for 30 seconds, and then reconnect and try the backup; can you get it to fail at this point? If not, your phone may be having issues either traveling from node to node, or from frequency to frequency.

There are a few other settings that can be altered to identify a cause of the disconnect, such as beamforming. Try reading through this article and then going through these settings over time to see if you can find one of the settings that will allow the backup to occur. If it is not a connection issue within your network, but rather with connecting to Apple's servers, try changing your DNS settings to a common service such as Google or CloudFlare to see if the backup can be completed.

Let me know if you are still unable to complete a backup and we can look into your settings further.

If this is the only abnormal behavior that you are experiencing, I would recommend potentially trying to set a schedule for the backup to a time at which you know your device will be stationary for a long period of time, such as during the night. Most phones have a sleep mode for their Wi-Fi antenna and if a backup were to wake the phone's connection, it might reconnect to the correct node using the correct frequency.