ID 414321 - Pressing TAB works every other time

Problem summary

Pressing TAB works every other time 

Customer reported version

mari.4.6v1

Customer reported platform

Steps to reproduce

1) Open the Example Head Project and go to the NodeGraph 

2) While in the NodeGraph try to press TAB to open the node browser 

result: pressing TAB works every other time 

Expected behaviour

Pressing TAB once should bring up the node browser 

Actual behaviour
Pressing TAB once no longer works 

Workaround
Press TAB twice 

Reproduced by support
This bug has been reproduced in:

4.6v1 - Windows 10 - CentOS7

4.0v1 - WIndows 10 - CentOS7 - regression

Unable to reproduce bug in:
3.4v4 - Windows 10 - CentOS7 

Earliest version tested
3.4v4 - This issue doesn't appear in this version and has regressed