[cups] "Aborting job because it has no files."

[Csermák Szabolcs]

Dear All,

I am facing to a serius problem.
We are using BOCA ticket printer, and sometimes the printing fails on 
ubuntu 16.04

On a successful print, I can see two lines in the cups access log, e.g.:

localhost - root [23/Nov/2016:13:07:44 +0100] "POST /printers/testfile 
HTTP/1.1" 200 330 Create-Job successful-ok
localhost - root [23/Nov/2016:13:07:44 +0100] "POST /printers/testfile 
HTTP/1.1" 200 808 Send-Document successful-ok

But sometimes the second line missing, so there is no "Send-Document". 
It is resulting in an error, e.g:

E [23/Nov/2016:13:22:37 +0100] [Job 14550] Aborting job because it has 
no files.

I have created a "copy" of this printer, and set it to print to file. I 
can reproduce the problem in this way as well. (BTW, the file does not 
created.)

What should I check?

Waiting for your answer,
Best,
Szabolcs