I took a look at your capx and I noticed you are changing the Z of the scenario. I change the Z of the character, putting it in front of behind the nearest scenario item. This way I don't mess with the original Z relation among scenario items.
By the way, do you know you can change the collision box for the player and objects? This way you don't need the green and red boxes you're using to check for collision. Just enter Edit Mode and click on the last tool button (Set collision tool).