I am using the latest versions of FCP and Compressor and both will not decode a video clip using Apple Devices 4K (HEVC 10-bit). I've been using this output for some time with no issue. The last attempt with Compressor generated "Failed: 34x Cannot Decode". After the FCP failures, I deleted the optimized and rendered files and created new ones. FCP failed again and exported the project so Compressor could do all the work, but that didn't work either.
The video has been decoded (shared) before and I'll I did since then was add chapter markers to it.
Possible issues and fixes?