break constraint not breaking as expected

I am working on a basic dismemberment system. I am using the break constraint node to sever the limbs. The problem I’ve encountered is that when I break the constraint of certain limbs, they seem to stay attached. From my limited experience, it seems to be related to the meshes armature itself, as it only happens to the two thighs and upper arms/neck. Here’s the armature I’m using:

Demonstration of the issue:

Any help will be greatly appreciated.

Update: Tried using the ue4 mannequin, works fine with it. Some of it must be to do with the meshes armature, but I don’t know what.

Since it works with the ue4 mannequin, is there some set way the bone structure is set up that I’m missing?