M4v video files verify non stop on iMac but will not play

Some files after converting from MKv to a format Quicktime will play such as m4v extensions, verifies non stop but will not play. Very annoying, buy it only happens now and then not to all converted video files ( I use Handbrake ) Of course it is a good idea to virus scan it. But renaming it to ( name ) . mp4 often works. Why this happens to some but not all converted video files I do not know. To date other suggestions to use Terminal to stop the verify process did not work for me. Hopefully this suggestion does help some, it did for me.