There is no bug, that I can see. You should really take the time to look at the manual and tutorials, and load the templates that come with C2. They are a great source of learning material.
The first problem is that your Layout uses the 'Control del Ovni' Event sheet, but the event sheet that handles collisions isn't even included. Press Right mouse and select 'Include Event Sheet'.
Secondly, The collisions sprite box 'Wall' just needs to be extended along the floor and collisions happen as expected, or change the collision event sheet to check for collisions with the FloorBackground object.