I have Just had a look at your cap, and would recommend that you use the 'Physics' behavior instead of 'Custom' for moving your crates. This will save you having to write extra collision detecting events, and will make your game look more realistic.
Step by step for crates
1, Remove the 'Custom movement for the crates and replace it with the 'physics' behavior.
2, In the crates settings, tick the use 'Gravity' box.
3, in the crates settings, set 'Collisions' to 'Bounding box'.
4, In the spite editor, move the crates collision point to the center of the box (12x12)
Step by step for the floor
1, Assign the 'Physics' behavior to the floor(to stop the crates falling through it)
2, DONT tIck the use 'Gravity' box for the floor, for obvious reasons.
3, In the floors properties settings, tick the box that says, 'Immovable'
4, in the floors properties settings, tick the box that says "solid"
5, In the Event editor, remove any leftover event lines concerning the crates custom movement.
if i have left anything out, or it doesn't work, you can download an amended cap here-