Failed: Video rendering error: -50 (ProMSRendererTool error -50: renderVideoFrame failed)

OSX 10.13.6

FCP 10.4.6

Compressor 4.4.4

Compressor keeps failing: Failed: Video rendering error: -50 (ProMSRendererTool error -50: renderVideoFrame failed)

There is no lookup table I can find for FCP/compressor errors. If, like other error messages posted, this means there is a bad frame, how do I identify the frame so that I can skip around it?

Thanks,

Joe