I am not sure how to explain this. Let me try. When I have an inventory item in hands, for example, a train rail, and I want to 'paste' it on the map many times, to make, for example, a long strait line.
I can do it from up to bottom (that is, my avatar going down and letting left button mouse engaged), bottom to top, left to right.
Every combination that does not involve the MOVE LEFT key works.
From the moment I use the MOVE LEFT key (that I remapped to the 'Q' french AZERTY key, which is 'A' in qwerty), the item diseappears.
Example with images :

Left image is what happens when I have the rail selected. For example I can move up, down, right, and the rail icon is still there in 'hands'.
When I move left, it diseappear.
I checked my controls, the 'Q' is only assigned to MOVE LEFT, and 'A' is not assigned anywhere (just in case).
I have the problem on Windows 7, and on another computer running Arch Linux.
Thanks for a great game !
I am dumb, can someone delete this post ?
Thanks !