HI, I have had this problem for years and hope somebody can shed some light on the cause.
I use Video Pad version 2.41. When I render into mp4, I occasionally get a problem in the video where the image distorts for one or several seconds (or even longer) and the colours run and the image 'melts', which is the best way I can describe it. It only happens in mp4; I have tried different output quality settings and re-editing the whole thing usually only changes the location that it occurs. Only some movies are affected, not all. It occurs on HD and medium definition, sometimes even low definition material. What happens is that the picture will suddenly freeze for a split second, then the image just melts in places while it is playing. I wouldn't call it pixelating but it is similar. The image playing loses all definition and the colours merge and run into each other. Sometimes it is barely noticeable, other times it destroys the whole video.
Has anybody had this problem? I wonder if it is just Video Pad somehow has corrupted those bits of data. But I wish I knew what caused it