Reported on UDN (see Additional Info URL). Looking at code, we call USkeletalMesh::AllocateResourceForRendering for every LOD, but we should only call it once.
Need to check if our SkelMeshMerge test case only has a single LOD, and that is why we didn't catch that?
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-59810 in the post.