Cloning tool not working

[jbang]

I'm running AfterShot Pro 2.3.0.99 on Kubuntu Linux 14.04.

I have had to straighten a (Canon RAW) photo I have taken, which gave me 2 grey corners, that I want to remove by cloning a part of the photo into the grey areas. But I can't get it to work.

I have followed the directions in the online manual ( http://product.corel.com/help/AfterShot ... clone.html ), and as long as the polygons do NOT touch the grey area at all the cloning works fine. But when I try to cover part or all of a grey area, then the cloning doesn't work.

I have uploaded a screen dump of what I'm doing (https://www.dropbox.com/s/k331dg2sr78nc ... m.png?dl=0). The blurring was done to the screen dump, NOT to the original photo. It was only done, because I don't yet have the model's approval of the photos (I'm still editing them), so I had to blur her out for now.

Can any one in here please tell me what I'm doing wrong?

Thanks in advance
Jens