One last thought... You said..."when I download video from the onboard micro SD card directly to my computer via a card reader the video pauses.."
So... you're COPYING the video file to your computer first, then playing it, right? You're not trying to play it directly from the SD card, right? If so, it will be terribly slow, and stutter, etc. The poor SD card can not read fast enough to play it, especially if it is higher than 1080.
I always copy the video to my computer then edit it in Final Cut Pro. Plays great before and after the edit. Just a thought.