Does not occur in 4.14.3 binary or 4.16 perforce.
Occurs in both P4 and Binary builds of 4.15.
Only occurs with Import Mesh LODs enabled and Import Animations disabled.
Result: Observe that extra skeleton and physics asset are generated
Expected: Only one skeleton and physics asset should be generated
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-40640 in the post.