Quicktime no longer opens my mov files

I am creating a movie, editing it in iMovie. Since I updated to Catalina I have noticed that my .mov files will no longer play in Quicktime - they will only play as audio. Thank God iMovie still recognizes the .mov files, I am able to import them with both the video and audio showing in iMovie. I'm thinking the upgrade from Mojave to Catalina updated Quicktime and with it, the codecs it used to recognize.

I am exporting out of After Effects as Quicktime with the default Animation codec. I'm wondering if changing the codec so Quicktime will read the exported mov's OK, will in turn screw up iMovie being able to recognize them. I've got a whole list of mov files that won't play, I would have to open and convert them all for Quicktime to play them. I don't know that to do - please help : P

Thanks,

Carl