When I print that appears in /var/log/cups/error.log
E [08/Jul/2015:15:23:27 +0200] cupsdReadClient: 15 IPP Read Error!
otherwise no error messages[/QUOTE]
it should list (not as errors) the filters applied to the job - likely starting with “texttops”. I suggest to run that filter chain manually, to see at which step the input is no longer processed properly. If this exhibits no problem, you might configure an additional filter (perhaps on a new “printer”) to capture the input that CUPS receives from the client, to see if the client sent the complete text at all.