> It's only once the project is done and viewed on a tv when it shows up.
The "epileptic seizure" can't be seen on a computer monitor. The problem has been there ever since you created the still; you just couldn't see it. When working with graphics, you should always check on an external TV/monitor. Effects - Video Filters - Video - De-Interlace will get rid of it, but you must check on an external monitor because you may have to switch the Field in the filter to "Upper" or "Lower", and there's no way to determine which one if you're using only a computer monitor.