Loss of file extension when copying between courses

[KevinKennedy]

I think this might be a one-time strange bug, but has anyone ever seen something like this before?

I have an instructor who copied some PDF from an old course, but they all came over without a .pdf extension. Students can still download the files and open them if they choose Adobe Acrobat as the "open with" option, but the files show as just "files" in their properties, and can't be previewed in Canvas. Plus, students don't always know how to use the "open with" successfully, so I've had to forward some additional instructions onward.

Again, I think this may be a one-time weird thing, but just in case: has anyone else ever seen this, and if so what was the cause/solution?

Thanks!