@Ashok,
Thank you for the suggestions. I tried all of the following, but none worked:
1. Latest Chrome on Mac with all caches cleared, standard browser window.
2. Latest Chrome on Mac, Incognito window.
3. Latest Firefox on Mac with all caches cleared, standard browser window.
4. Latest Firefox on Mac, Private window.
I am still unable to delete any Port Forwarding entries. And, of course, port forwarding itself is not working. Some pictures attached, but not sure how useful they will be...