Lines missing from Word print jobs

I have a vbs script that automates our daily report printing that calls a macro in Word and prints files to the default network printer. Every so often, the reports will be missing lines at the bottom of the page, seemingly at random. It’s very embarrassing to hand over reports to your boss that are missing important information!
All the macro does is open a text file, format it and print to the default printer… a re-run of an individual file will usually produce the correct report, as the underlying files are not affected.
Is there any reason a print job will just randomly decide it doesn’t want to print some lines?