copyAssetsVideoIOS converts MP4 to (really big) thumbnail

I have MOV and MP4 videos in my camera roll which I need to upload. However, copyAssetsVideoIOS() is turning my MP4 files into thumbnails (which actually have more kilobytes than the original videos...).

Is there somewhere in the XCode project I can fix this? Or has someone already addressed it in a different branch?

Thanks.

PS. I accidentally used copyAssetsFileIOS once which didn't convert the MP4, but the uploaded filesize didn't match the local file size so my backend rejected it as bad data.