ID 416535 - Sporadically drag and drop images into the Image Manager stops working - MATE specific

Problem summary

Sporadically drag and drop images into the Image Manager stops working (MATE specific)

Customer reported version
mari.4.5v2

Customer reported platform

Steps to reproduce

1) Open Mari and example project 

2) Open the image manager as a floating pinned palette 

3) Drag and drop any image from a folder to the image manager 

result: Sporadically it does not work. 

Expected behaviour
It should load the image 

Actual behaviour
It does not load 

Workaround
Try loading it again 

Reproduced by support
This bug has been reproduced in:

4.6v1 - CentOS 7 (MATE)

4.5v2 - CentOS 7 (MATE)

Unable to reproduce bug in:
4.5v2 - CentOS 7 (Gnome)