I'm having a strange problem here: basically, whenever we send a newsletter, only the plain-text part appears. I have checked with the SMTP gateway and the emails it is sending out are the same as the ones CiviCRM is sending. Additionally, when I click the "Preview as HTML" button, a new window appears which is blank except for the text "(null)".
Nothing really has changed except I think a routine upgrade (to 4.7.29). We also emptied the templates_c directory a few weeks ago because it was over 8GB+ in size. In any case I've tried refreshing caches (using URL, dashboard button and drush methods), and loading, modifying and re-saving the newsletter template.
Additionally, I can no longer see contributions on a contact's dashboard (though the number of contributions is correctly displayed). I don't suppose that's related..?