Port Forwarding no longer works, and cannot be configured via 10.0.0.1

Recent firmware upgrades have made it so that the Xfinity router interface available through 10.0.0.1 no longer allows you to configure port forwarding.  Instead, a box tells you to go to xfinity.com/myxfi.  Unfortunately, even that doesn't work.  I can configure a port, or a port range, and it works once, but then it stops working.  I have been on the phone with support for roughly 12 hours over the last five days, and at the end of it they told me they were going to report it.

This used to work until they forced me to swap out my modem for a TG1682G.  That's the first one that no longer supports changing port forwarding via 10.0.0.1.  My working port forward stopped working and I had trouble configuring others.  Next they told me to swap for a TG3482G, which I did but the same issue occurs.

So right now port forwarding doesn't work and Comcast says they don't know why.  Does anybody have port forwarding working with a TG3482G?