ID 502458 - Write node doesn't correctly read multichannel files when they include reserved channel names

Problem summary
Write node doesn't correctly read multichannel files when they include reserved channel names.

Customer reported version
Nuke 13.1v2

Customer reported platform
CentOS 7

Steps to reproduce

1) Open Nuke and create a Colorbars node.

2) Create a Shuffle node and connect the Colorbars node into the Shuffle node.

3) Open the Shuffle node properties, change the Output Layer to mask, and then connect the rgba.red from the Input channel to the mask in the Output Layer.

4) Create a Write node and connect the Shuffle node into the Write node.

5) Open the Write node properties, change the channels to all and turn on the read file option

5) Create a Blur node and connect the mask output from the Write node into the Blur node.

6) Open the Blur node properties, change the size to 99

7) Create a Noise node and connect it to the Blur node.

8) Open the Noise properties and change the x/ysize to 1

9) Connect the Viewer to the Blur node then in the Write node properties turn the read file option on and off.
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Expected behaviour
For the Write node to correctly read multichannel files when they include reserved channel names.

Actual behaviour
The mask layer is not passed through the Write node correctly, there is also an additional mask_extra.alpha node created.

Workaround
Uknown.

Reproduced by support
This bug has been reproduced in:
Nuke 13.1v2 - Windows 10 - macOS 10.15 - CentOS7
Nuke 12.0v1 - Windows 10
Nuke 11.0v1 - Windows 10
Nuke 10.0v1 - Windows 10
Nuke 9.0v1 - Windows 10 - macOS 10.15 - CentOS7

Earliest version tested
- This issue appears to be in all versions of the product