I’m attaching a actor to a component at runtime, that component is in my player blueprint and is part of a physics constraint. When detaching the actor that I attached previously that actor won’t have any collision anymore, I can’t trace it and I can’t collide with it.
I just tried something as a workaround and found another bug, this one crashed the editor:
I added another component and put that inbetween, so that is attached in the player BP to the component that is physics constrained. On top of that I attached the actor at runtime, then to detach I didn’t use a detach node and instead deleted the component that was inbetween which just crashed everything. 
Turns out the bug (and crashes) occured because of the actor that I attached had a arrow component as the root. My guess is because the root has no collision it does break it.
Turns out I keep getting bugs and crashes, just different ones. There is something seriously messy with Physics Constraints. There is one bug where the trace collision remains its location when I change it while the mesh and physics collision changes and that is after I detached it from a physics constaint object. Then there is a bug that crashes the engine when I change physics of a physics constraint object.
I only need to have this bug fixed now, but it might be rather tricky to fix: https://answers.unrealengine.com/questions/227900/bug-quantum-physics-collisions.html