Missing (delayed) file

We have a software vendor that is using PDF Creator 2.1.2 to generate pdf files from one system for import into their system. This is the process as I understand it so far:
We select a Custom PDF Creator Printer profile in one system.
Click Print
This generates 7 pdf files into a folder on the workstation. We get little screen flash/pops as the pages are "printing".
Then in their system we click an import button that goes out and grabs all pdfs from that holding (target) folder and brings them into the persons record in their system.
The pdf files are then deleted from the holding folder (automatically)

I found their "Profile" in PDF creator and everything seems pretty straight forward. They use a counter token on the filename, they have a target folder setup. That's basically it from the looks of it.

The problem is, sometimes we are missing a page (the last one). There's only 6 there. Occasionally it shows up after a few seconds. I had initially thought they were just going too fast since they have dual monitors and are in both systems all the time and maybe they were just hitting import before the last file finished processing. But other times it just never arrives! I can delete the other files from the folder, sit in the there for minutes refreshing and nothing. But when you go back and try it again, the missing page then shows up with the next batch. So instead of 7 files, you now get 8. If they don't catch it, it leads to 1 page of a clients file getting put into the next persons record. Usually nobody would be babystiitng this process and watching, we've just learned what is happening as we troubleshoot by watching the target folder.

It seems this file is just kind of stuck somewhere. I mean it eventually arrives with the next batch so it is somewhere.

The vendor (and another customer of theirs I talk to that experienced it) basically just say, try re-installing their software & PDF Creator, try clearing temp files, disk cleanup etc.....reboot.....

We have been instructed not to use a higher version than 2.1.2 currently due to some other issues apparently. I just installed their software and PDF creator on my machine for testing 2 days ago, and can occasionally replicate the issue, maybe not as often as on my users laptop but it happened. So I doubt reinstalling software that has been installed for less than 48 hours is a part of the ultimate solution here.

Can anyone provide an guidance on where the missing page/file could be? What I can try to further troubleshoot or better yet ask them to try?