My son is capturing Xbox gameplay with an Elgato HD capture card. He  then imports into Movie maker. Then he saves, within movie maker, to high definition display to upload to youtube. Everything has been working fine for weeks.

Suddenly yesterday, when saving to high definition, it began doubling the file size by actually duplicating his video clip in the file.

How do I stop this from occurring? I already uninstalled/reinstalled Movie Maker today.

Thanks in advance for any ideas.