FCP crashes on exporting 300fps timelapse

I recorded a series of screen captured timelapses and when joining them in FCP and trying to export, FCP fails to do that, just crashing or saying "can't refer frame at xx.xxx.xxxx"

I've: erased preferences, removed and reinstalled fcp, moved clips to a new project but nothing seems to work, so I came to the conclusion that the trouble must be in the original captured Timelapse.

If I try to transcode the media, fcp says that I do not have enough disk space, which sounds odd, considering file size and availability on my drive.

any Ideas? thanks in advance

I attach footage specs

MAc os 14.6.1 , FCP up to latest version