Thank you!
Yes, i tried to rework and simplify collisions masks during the extended time we had for the submission, but it didn't really work! At this time, i can't tell why collisions are so buggy. :/
Technically, they are: it's just the sprite that broke remade in particles. There is only a resize of the original 30x30 sprite into 5x5 sprite by Construct 2. :)