Xfinity Gateway Port Forward Incorrect IP

Here's a summary of the issues I've been having over the last few months with port forwarding through my Xfinity Gateway:

• Port forwarding cannot be set up through the default gateway, as is standard with other modems. Instead, Xfinity sends you to "xfinity.com/myxfi" to set up port forwarding.
• Sometimes the device I'm trying to set up port forwarding for is not shown in the "Connected Devices" list.
• Sometimes the device is shown in the "Connected Devices" list, but shows the wrong IP address for the device.
• Sometimes the device is shown in the "Connected Devices" list with the correct IP address, but when setting up port forwarding for the device, a port is opened on the wrong IP address.

I've already tried the following actions to fix the issue with no luck:

• Attempting to set up port forwarding through the Xfinity mobile app.
• Attempting to release and renew the IP address on my device with ipconfig/release, ipconfig/renew.
• Disconnecting and forgetting the device on "xfinity.com/myxfi", then reconnecting the device.
• Using all of the "Reset/Restore Gateway" options in the troubleshooting tab of the default gateway.
• Unplugging the gateway from power for several minutes, then plugging back in.
• Several combinations of the above actions.

It seems like when one issue randomly fixes itself, another pops up. I've read that many customers have been having the same problems for years, with no clear solution. How is this not fixed yet? Seems like the only proper solution is to buy a 3rd-party Xfinity compatible modem and router that gives you proper control through the default gateway.