could this be a corrupt file?
Don't know.
One way of testing for problems could be to run the file through
MKVToolNix. From what I know, it defaults to do a 1:1 transcode from whatever video container to mkv. I'm pretty sure I've done this when I've had dodgy vid files before but can't be sure.
If the process goes through with an error code of "0" and the file plays without hassle, then great. If not, the software is freeware, so you've not lost out. There maybe diagnostic software out there. If you find one that's useful, let us know.