OpenPGP header url for mail.bitmask.net is broken

The OpenPGP header for mail.bitmask.net looks like:

Openpgp: id=4BE5E7FE0E49ADA6; url="https://bitmask.net/key/fptest";
 preference="signencrypt"

The url should be "https://mail.bitmask.net/key/fptest" and it seems to be correct sometimes but not always, what is wrong here?

(from redmine: created on 2016-05-05)