Live Movie Maker - Windows 10 - Yellow Triangle - Error 0x87160139

That's extremely frustrating. Fortunately I haven't encountered that personally, but I have seen others with similar symptoms. About the only solution I've seen mentioned that works is to convert the problem files to .wmv format. But I know that then means all your edits are lost and you have to rebuild your timeline.

One possible way to "trick" Movie Maker into working with converted files is to rename them to the same extension and location as before.

If you want to try this, I would do the following. First make a copy of all your source files (.MOV files) used in the project. Also make a second copy of your project (.wlmp) just in case.

Now convert them all to .wmv format using something like Freemake Video Converter (if you choose this freeware converter, be sure to choose a custom install an uncheck everything it wants to add-on).

Once the files are converted (in a different folder), rename them to have the same name as before, but with the .MOV extension. Now reopen your project and when it shows the yellow triangles, double-click on one. Instead of linking to the original .mov file, navigate to the folder with the "fake" converted .mov files. See if that doesn't fix the links and let it work after that.