What problem? Complex Collision is static and cannot be simulated.
if we have a bunch of immovable craggy rocks players needs to navigate on with a high degree of fidelity, and one cannot be arsed to laboriously craft neat collisions, use Complex as Simple
if you need something to move, rotate, simulate, interact with other entities or be overall performant, stick to Simple Collision. There’s a bunch of different ways to get the correct collision shape: