ID 510807 - Sub-Menu timeouts are inconsistent across different sub-menus

Problem summary
Sub-Menu timeouts are inconsistent across different sub-menus
 
Customer reported version
Mari 5.0v3
 
Customer reported platform
Multiple
 
Steps to reproduce
 
1) Open any project

2) To make this issue more apparent, set the Sub-Menu Timeout value to 500 (Preferences > Misc. > Appearance > Sub-Menu Timeout)

3) Open the right-click context menu in the Canvas, then open the 'Visibility' sub-menu and move your cursor quickly and diagonally downwards onto the sub-menu
 
4) Open the right-click context menu in the Node Graph, then open the 'File' sub-menu and move your cursor quickly and diagonally downwards onto the sub-menu
 
5) Compare the behaviour between steps 4 and 5
 
Expected behaviour
Both sub-menus should stay open as the cursor is moved across to them
 
Actual behaviour
For sub-menus that have a 'separator' below them within the parent menu (e.g. the 'Visibility' sub-menu in the Canvas context menu) the sub-menu will stay open until the cursor reaches the target. 
However sub-menus that do not have a separator below (e.g. the 'File' sub-menu in the Node Graph context menwill close before the cursor reaches them and the sub-menu below will be opened instead - even with a Sub-Menu Timeout value of 500 (shown below):
 

 
Workaround
Unknown.
 
Reproduced by support
This bug has been reproduced in:
Mari 5.0v3 - Windows 10 - CentOS 7.9
Mari 4.8v3 - Windows 10
Mari 4.7v7 - Windows 10 - CentOS 7.9
 
Earliest version tested
Mari 4.7v7 - This feature did not exist before this version