When you resize the window, by default the contents are stretched to map the new size. Which means that the default view no longer maps to the window size, and that you must call the mapPixelToCoord / mapCoordToPixel functions whenever you need interaction between the scene and the window (mouse).
Since you give no detail about what you do on resize, how your collisions work, and what exactly happens when the problem occurs, there's nothing more we can say.