Issues with mp4's rendering black video

Hi,

so the issue im having is that on the PP timeline when i import and place a video file it can play both audio and video. yet when i go to export it only the audio comes out and the video is completely black.

i've changed the renderer from mercury Playback engine GPU acceleration (Cuda) as defualt to the Engine software only and back with no changes to the export. ive updated drivers. i've checked the sequence settings too. exporting as MP4 in H.264 format changing this doesnt make any difference. system resources are not low. Also other video files work fine when exported in the same project and the files im having issues with export fine on another application (ncn).

any advice?

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