Why doesn't CUPs print all pages?

Question

linux

There is a server with Ubuntu. It has CUPs and a Brother laser printer attached. Sending to print from the client directly works fine.
There is a script that checks the contents of a folder and, if a file appears there, sends it for printing.
In 95% of cases everything works fine, but in 5% the printer does not print all the sheets.
Here is the last case. There are 41 sheets in the file, pdf file. The weight of the file is 6828k, the list of completed CUPs tasks has this file and the size is correct, but the number of printed sheets is 21.
What could be the problem?

Answer 1

Caps prints error logs here /var/log/cups
Look at the latest events there.