ID 427430 - Rendering DNxHR MXFs from Nuke gives the wrong result on both options for the output range (Full Range and Video Range)

Problem summary
Rendering DNxHR MXFs from Nuke gives the wrong result on both options for the output range (Full Range and Video Range).

Customer reported version
Nuke 12.1v1

Customer reported platform
macOS 10.13 (High Sierra)

Steps to reproduce

1) Open Nuke 

2) Create a ColorBars Node and connect it to a Write node.

3) On the Write node, set the file path, set the file type to mxf, and set the colorspace to rec709.

4) Set the output range knob to Full Range and render the script.

5) Set the output range knob to Video Range and render a second mxf.

6) Read both clips and view the result.

Expected behaviour
The "Full Range" clip should match the original comp.

Actual behaviour

The "Full Range" doesn't match the original comp.

The "Video Range" clip isn't noticeably different from the original comp, however, the RGB values are slightly off.

Workaround
Unknown.

Reproduced by support

This bug has been reproduced in:
Nuke 12.1v1 - Windows 10 - Linux CentOS 7 - macOS 10.15 (Catalina)

Earliest version tested
Nuke 12.1v1
- Writing MXFs was not supported in Nuke prior to 12.1v1.