ID 438929 - Selecting a Backdrop node also selects nearby, non-intersecting nodes above and below it

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Problem summary
Selecting Backdrop nodes will also select nearby, non-intersecting nodes above and below it

Customer reported version
Katana 3.6v1

Customer reported platform
CentOS 7

Steps to reproduce

1) Create a Backdrop node

2) Create another node, that is not a Backdrop, and place it close to the top or bottom of the Backdrop node, but not intersecting

3) Select the Backdrop node

Expected behaviour
Backdrop is the only node selected

Actual behaviour
Backdrop and nearby node is selected

Workaround
Unknown.

Reproduced by support

This bug has been reproduced in:
3.6v1 - CentOS 7 - Windows 10
3.5v3 - CentOS 7 - Windows 10
3.5v1 - CentOS 7 - Windows 10
3.2v4 - CentOS 7 - Windows 10
3.2v1 - CentOS 7 - Windows 10 - Regression

Unable to reproduce bug in:
3.1v1 - CentOS 7 - Windows 10

Earliest version tested
3.1v1 - This issue doesn't appear in this version and has regressed

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