Blender-exported Skeletal Meshes Freak Out in the Physics Asset Tool

This is a problem I’ve had for a long time, and as a result I’ve never really been able to get physics assets working on my skeletal meshes. When I import a skeletal mesh from Blender and auto-generate a Physics Asset, this is what the simulation looks like:

All of the bones immediately fly into each other and the whole character bounces around wildly. If I delete all of the capsules and start from scratch, this happens as soon as I have two adjacent capsules:

For whatever reason, the thigh capsule immediately pops to a location far away from the pelvis; adding more capsules just exacerbates this issue.

I managed to find a workaround of sorts, by using Mixamo to rig the mesh; even after I made a few adjustments to it in Blender (rotated some of the bones, changed the weightings a bit, reparented some bones) and exported it, the physics asset behaved in a much more sensible way, which ruled it out as an issue entirely to do with Blender’s FBX export. In order to make animation easier, however, I’ve had to make more changes to the skeleton, and now the same old issue is happening. Considering I haven’t seen anyone post about a similar issue that wasn’t caused by something I’ve been able to rule out, I’m really confused as to what it is I’m doing wrong.

In the screenshots above, the LegControl.L and R bones are the new IK control bones that I added; I’m only exporting deform bones from Blender, and these are set to non-deform, but they’re still making it in, possibly because the rest of the foot bones are parented to them. At any rate, if I delete them (and the rest of my IK bones), the same issue occurs. The IK bones at the top of the tree were generated by Mixamo, and they were present in the version of the model that was working correctly. Even so, if I delete them all and re-export the mesh, the same issue occurs.

So I’m completely stuck, and would really appreciate any help! The mesh I’m working with is here: https://dl.dropboxusercontent.com/u/3250291/Games/SKM_BusinessGuy2.fbx

I posted my work around here ( Blender to UE4 Skeletal Mesh Explodes with Seemingly Multiple Roots) In my project it works about 80% of the time, and the other 20% is difficult to fix, but usually involves messing with the bone hierarchy in blender.

Hope this helps!