ID 176518 - Selecting a channel with Wacom sometimes selects the channel below

Problem summary
Selecting a Channel with a Wacom table often selects the channel below
 

Customer reported version
3.4v1

Customer reported platform
10.13

Steps to reproduce

1) Open any project in Mari on OS X

2) Using a Wacom tablet, navigate to you channels palette

3) Select one of the channels

4) Often the channel below is selected. Though this is sporadic:
 

Workaround
Unknown. 

Reproduced by support
Mari 3.4v1 - OS X 10.12.4
Mari 3.3v1 - OS X 10.12.4

Earliest version tested
Reproduced further by developments (3.0 series)
 

Expected behaviour
To be able to accurately select the channel you are clicking

Actual behaviour
The channel below is sporadically selected