From what I'm seeing, it seems specific to QTP and iMovie. It works perfect in VLC for instance.
No updates on both OS, just the regular Garmin software updates (can't really remember which version must have changed this behaviour if it's related to Garmin).
I had this same problem with my Garmin Dashcam 55, but I found a fix/workaround for this! Check out my solution in this Garmin Forum post: forums.garmin.com/.../1392753
