Replace Original with h264 Feature not Working.

I am having an issue with the replace original video with h264 feature. It sometimes replaces the video with the encoded one, but the majority of the time it does not replace the original.

When I go into uploads folder and look at it I see that -fullres.mp4 is still sitting there and just was never replaced/renamed to overwrite the original. If you could please help me debug this issue that would be great.

Thank you.

https://www.ads-software.com/plugins/video-embed-thumbnail-generator/