Platform and Physics behaviors do not work together. If you want an object to follow another you can use the Pin behavior, or just every tick set object1.X and Object1.Y to Object2.X and Object2.Y...
IF you don't want them to be right ontop of eachother you can do object 2.X+10 or something like that...
You could also do something like set angle (object1.X, Object1.Y, Object2.X, Object2.Y) if you are using the bullet behavior...