I have a similar problem. I can load several video files (both .mp4 and .m4v) without an issue. But there is one file .m4v which loads but only the audio track is working. The video track is solid black. I am able to play the file directly. Using Win10.Videopad version 8.06.
I tried deleting the files from "C:\Users\<your user name>\AppData\Roaming\NCH Software\Components" as described above but it did not fix my problem.
Any ideas on what else I can try?