There are several features on Ancestry and Newspapers which don't work via the proxy. For example, in the family-tree viewer the "Media gallery" and "Family group sheet" options send you to a 404 page. More seriously, trying to view an Ancestry user profile also results in a 404 while on Newspapers user profiles are viewable but attempting to Follow a user (Following is apparently necessary to contact registered users through their profiles) brings up a login prompt for an individual Ancestry or Newspapers account. I don't know whether it's worth trying to figure out how to report all this, or if it's all just considered (not)-working-as-intended.