Windows do not 'snap' to the edges correctly

[Nuc1eoN]

I have lived with this issue for a while now, but it seems there is some bug when 'snapping' windows to the screen edges (e.g. make them fill half the screen).

For instance when opening a new terminal, and then pressing Super+Left-Arrow the window fail to stick to the left screen edge.
On a second attempt it works!

I suppose the issue is somewhere in the awesome configuration.