As I mentioned above (altho perhaps not clearly), it's multiple servers, and it's occuring across all servers.

The code in the content type handler is fairly simple, and given that it works in the vast majority of cases, I'm not so suspicious of it:

sub type_handler {
   my $r = shift;

   my $type = $r->notes('CONTENT_TYPE');
   if ($type) {
      $r->content_type($type);
      return OK;
   }
   else {
      return DECLINED:
   }
}
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What sets the content type in the notes? That's done in the translation handler, read from a file for each piece of content it serves. I can be fairly sure that this is being done correctly for the cases that content type is being set to text/plain. (I haven't ruled it out, but if that *is* the problem, then it's not likely I can get much help from PM without going into a *lot* more detail, which I'm probably not prepared to do at this stage).