Question: Are you setting up the collision objects as static meshes?
If yes, then that's the problem. There is a bug whereby if you position, rotate or scale an object in DBP, prior setting it up as a static mesh, collision will not work correctly. It seems that the visual object is changed but the collision data is not.
Until it is fixed (
), the workaround is to scale/position/rotate the object in your 3d modeling application, and once you load it in DBP, set it up immediately as static mesh.
Theory is when you know something, but it doesn't work. Practice is when something works, but you don't know why.
Programmers combine theory and practice: Nothing works and they don't know why.
