The issue we saw was JDE truncating the version on job names, instead of something less meaningful, like the job number. For example, R5542565, version CP0009SC, job number 1234567 became R5542565_CP0009S_1234567.pdf. We would have preferred that it truncate from the right, not the middle, so that the name would be R5542565_CP0009SC_123456.pdf. But then, that would make sense, explaining why it wasn't done that way.
If allowed to go on too long, I can see how this could result in invalid MBR names, since they might easily exceed 10 characters. We check the next job number on our system periodically, and reset it to a much lower number when it gets above about 950,000. That's easier than dealing with the problems that start cropping up when the job number reaches 7 digits.