SW2015 2.1

I stumbled across an assembly created by someone else where the order of items in the feature tree is unusual:

Somehow, a bunch of components ended up between two component patterns, after the Mates.  Furthermore, notice that LocalLPattern7 is a pattern of the component below it (409107).  I can roll back the feature tree to before LocalLPattern8, but I cannot roll it back anywhere between the misplaced components.  It will roll back to before LocalLPattern7, but misplaced components are still fully accessible and aren't greyed out.

If I drag all the misplaced components to where they would normally be (before the Mates folder), I cannot return then to their original incorrect positions.

I'm curious if anyone else has had this problem and knows if it is a file corruption issue or something else.

JIm S.