ID 383423 - Painting multiple small strokes with certain brushes makes Mari slow and unresponsive

Problem summary
Painting multiple small strokes with certain brushes makes Mari slow and unresponsive 

Customer reported version

4.2v2

Customer reported platform
windows10

Steps to reproduce

1) Open Mari and an example project 

2) Open the Shelf palette>Brad's New Brushes and pick the CurlyQ brush

3) Try to paint fast multiple dots on the model 

Result: FPS drops below 1 and there is a significant slowness 

Workaround
Unknown.

Reproduced by support
This bug has been reproduced in:

Mari 4.2v2 - Windows 10

Mari 4.1v1 - Windows 10 

Mari 4.0v4 - Windows 10 

Mari 3.4v1 - Windows 10 

Mari 3.3v1 - Windows 10 

Mari 2.6v5 - Windows 10 

Unable to reproduce bug in:

Mari 4.2v2 - CentOS 7 

Mari 3.4v4 - OSX 10.12.6

Earliest version tested

2.6v5 - This issue appears to be in all versions of the product

Expected behaviour
Mari to perform as expected

Actual behaviour
FPS drops below 1 and there is a significant slowness when painting multiple dots