MultiWayBlend anim node doesn't apply additives correctly

It seems that the MultiWayBlend node isn't applying additives correctly.  In the attached project are two anim bps, one which dynamically creates an additive and one which uses an additive sequence.  Both are blended with additive identity using the MultiWayBlend (seems to be the intended base pose to blend onto with this node) and then applied using the ApplyAdditive node.  In both cases, the results of the MultiWayBlend, the resulting output pose doesn't match the pose from which the additive was generated.

My guess is that this is due to the use of 
FAnimationRuntime::BlendPosesTogether to blend the additive poses.  Disabling the ispc codepath doesn't change the behaviour.
 

1. In the attached project, open 00553358_AnimBP
2. Note how the pose watch on FF_Walk_F doesn't match the output transforms despite the setup of the graph
3. Disconnect the MakeDynamicAdditive from the input to the MultiWayBlend and instead connect it directly to the Additive input on the ApplyAdditive node
4. Compile and note how the output transforms now match the pose watch on FF_Walk_F