World Space canvas with button is ignored if it is overlap with Screen Space - Overlay canvas

Hi,
I am trying to make mobile touch control with image on the left side for walking and image on the right for looking. Canvas is set to Screen Space - Overlay.
I have a World Space canvas with a button in a scene.

When I touch on the walking area I can click the button. But when I touch on looking area I can not click the button. I noticed that I can click the button if the image for looking is above the walking image in the hierarchy.

I tried adjust objects blocking, blocking mask and sort order. Nothing helped. Do I something wrong or is it a bug?

Thanks.

 

Hello,
I have also the same problem.

 

Nobody?

 

May be related to this thread - http://forum.unity3d.com/threads/graphic-raycaster-used-to-have-a-priority.283851/

Also, any reason you are using a world space canvas for that scenario?, another overlay or even a SS - Camera canvas would seem to be better suited

 

Thanks. I am using world space canvas for a 3d computer model with a touch screen.