Hi I have made this cool plane with really cool (and functional) fowler flaps. They look and work except for one problem. When fully extended, for some reason, they like to collide with the ground, however visually, there is no part of the flaps contacting the ground, in fact it is miles away from the ground, but still manages to make contact. I really cant figure out why.

here is a link to the plane in question.

I worked really hard on the wings i really want it to work