"Failed" status when bulk loading some enrollments

Summary

I receive a circle/slash "failed" icon for "Status" in BL results, with no further info, and usually not all enrollments load.

Content

Is anyone else seeing this? I bulk-loaded sessions and enrollments ILT for a couple of years before this started happening, but a few months ago I started getting a "failed" status upon uploading enrollments at times, with no other information. Usually, it means that all the enrollments posted except for the last one, which I then have to manually add. Sometimes I get this message when I uploaded a single enrollment, and it actually loaded fine. At other times, it only loads the first one! When I delete the row of the enrollment that did upload from the text file,