Video rendering error -50

Hi all,

Was editing my video with proxy media, changed it to optimised/original for the export, and I've came across an issue I've never had before. Lot of black frames in the project that take ages to load, but everything's there, it's fine though as I'm only trying to export, not edit. However, when I go to export it, that's where the real issue arises.

It's a 9 minute long video, normally this takes ~30min max, but this time it's been taking HOURS to reach 50%, and shortly after that the render fails, giving me the message:

"video rendering error: -50 (final cut pro error -50: renderVideoFrame failed)"

I am running Final Cut version 10.4.5, and macOS Mojave 10.14.5.

Any ideas as to how I could fix this? I've deleted preferences, deleted generated render files, created new projects etc. multiple times.

Please let me know anything that might help.

Many thanks!