I have a list of 36 contacts. When printing labels using Primary address it only prints the first 14 (first based on contact ID number, not alphabetically). When printing labels using Home address it prints all of them. All contacts have home addresses, all set to primary. Nobody has any contact restrictions. An export from the address table showed no commonalities between those that did or did not print other than the order of their contact ID number. This problem seems to be new/unique to 4.7.23 (Drupal) as far as we know (ie we didn't notice it happening before). The 4.7.25 sandbox does not seem to have this same quirk.
Summary question: What would cause Civi to print labels for only a subset of valid, mailable addresses?