The DNxHD format is very restrictive regarding the input frame sizes and frame rates it supports. This can result in problems transcoding from some source files.
For example, the DNxHD format does not support 4K resolutions, so attempting to transcode 4K source media to DNxHD will result in an error. Similarly, non-standard frame sizes (1280x960 for example) will trigger errors. This is a limitation of the DNxHD format itself.