I try to export a video with a mix of 4k and 720p film clips (including a single still Photo). When I export in HD 1080 p (29.970 fps) everything goes fine, but when I try to export in 720p (29.970 fps) to get a better presentation of the non-HD clips in my sequence, VideoPad crashes after a short time 'because of an abnormal exception'. Any ideas about what the problem could be? I'm using VideoPad 7.01.