Having Trouble With "Worm" T_T Tutorial

hey everyone, Im having a big problem with the worm, i'm on video #11 and every time i enter "Play mode" the worm flies around the map in a random formation, defying gravity and then eventually falling through the ground?? Please help someone.

Update: I have found that I am rotating around one of my placed turrets... does anyone have any suggestions to stop the problem or what i did wrong with it?

Sorry everyone XD, fixed it. Worm was linked with the turret.