[I've encountered similar issues, e.g. where I had entered my home address on Amazon using a format which at some point started being considered "invalid" by their input-validation code. The old address remained in the system (and worked fine when ordering), but I couldn't change any other personal info without also re-entering that address, because the input-validation wouldn't accept the old one (it apparently still validated all the old data at that point, even stuff I hadn't changed). Unfortunately the new system was much more restrictive about what it allowed in addresses, so I didn't want to... >< ]
[I've encountered similar issues, e.g. where I had entered my home address on Amazon using a format which at some point started being considered "invalid" by their input-validation code. The old address remained in the system (and worked fine when ordering), but I couldn't change any other personal info without also re-entering that address, because the input-validation wouldn't accept the old one (it apparently still validated all the old data at that point, even stuff I hadn't changed). Unfortunately the new system was much more restrictive about what it allowed in addresses, so I didn't want to... >< ]