I ripped a bunch of Blu-Ray discs using MAKEMKV and HANDBRAKE and most stream fine from iMac to ATV3. However, 2 of them don't seem to start playing. At the bottom timeline, where the progress of the movie is shown, you see the spinning spokes and a GRAY progress line, but no movie shows up even after 10 minutes...The others start within seconds. Any idea why this may be. Thanks.