I'm a total nube to this KDL, so not even sure if I'm posting in the right place.

A customer sent me a clean MP4 produced by another company. As a favor, I edited out a few seconds and re-rendered it as an mp4
Across the video, in sporadic ways the word "INVALID" is across the video. I have NO idea why.
I've done several NEW projects that don't have this. Sometimes in windows explorer, it also shows there, just clicking on the file. Sometimes not. VERY inconsistent.

Fixed below--->

KDenLive 20.12.1 Windows 10

In case anyone has this issue, I tracked it down to transferring files from the client's ONE DRIVE account to mine. Something got lost in translation. I re-downloaded the client's video to my desktop, did my editing and the issue went away.