ID 371962 - The 'shutter offset' option on the ScanlineRender does not offset the shutter open and shutter close time equally

Problem summary
The 'shutter offset' option on the ScanlineRender works unexpectedly when set to 'custom'. It should offset the shutter open and shutter close time equally.

But the offset sometimes affects only one end of motion blur which is like what the 'shutter' setting does.

Customer reported version
nuke.11.2v3

Customer reported platform
centos7

Steps to reproduce

1) Open the attached script in Nuke.

2) On the ScanlineRender node, go to the MultiSample tab and Adjust the 'shutter offset'. Notice that the shutter open and shutter close time are not offset equally.

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Reproduced by support

This bug has been reproduced in:
Nuke 11.2v4 - Windows 10 - macOS 10.14 (Mojave) - Linux CentOS 6

Nuke 11.2v1- Windows 10

Nuke 11.1v6 - Windows 10

Nuke 11.1v1 - Windows 10

Nuke11.0v4 - Windows 10

Nuke11.0v1 - Windows 10

Nuke 10.5v7 - Windows 10

Nuke 10.5v1 - Windows 10

Nuke 10.0v6 - WIndows 10

Nuke 10.0v1 - WIndows 10

Nuke 9.0v9 - Windows 10

Nuke 9.0v1 - Windows 10

Nuke 8.0v7 - Windows 10

Nuke 8.0v1 - Windows 10

Nuke 7.0v10 - Windows 10 - macOS 10.14 (Mojave) - Linux CentOS 6

Earliest version tested
Nuke 7.0v10
- This issue appears to be in all versions of the product

Expected behaviour
The 'shutter offset' setting should offset the shutter open and shutter close time equally.

Actual behaviour
The offset sometimes affects only one end of motion blur which is like what the 'shutter' setting does.