Preview/quicklook not working after Mojave update

After updating to Mojave recently, I can no longer preview (quicklook? don't know the technical name) video files. Regardless of format, used to be able to press spacebar on any video file to watch it in preview. It worked previously with all the main video types I use in my editing process: .mov, .m4v and .mp4 and now it doesn't work with ANY video files no matter the format. All I get is a freeze frame and I have to open the video in quicktime to play it. This drastically slows down my workflow when editing larger projects. Any ideas?

If rebooting the computer does not sort the issue, I would re-install the combo update 10.14.3 on top of your existing macOS. this is has been known to sort unexplained anomalies like yours.

Download macOS Mojave 10.14.3 Combo Update - Apple Support

There was a link posted above (?)

Download macOS Mojave 10.14.3 Combo Update - Apple Support