Not sure what to call this,
I think your mirror modifier has something to do with that but it is hard to tell.
Perhaps object transformation data between object and edit mode and perhaps object origins and/or mirror object references is/are doing that.
Definitely looks like mirror behavior though.
Thanks, although it doesn't adversely affect my model it's good to know why this is happening.
I think this is the same issue as described here: https://cgcookie.com/questions/10368-mirrored-linked-objects-flip-in-edit-mode-vs-object-mode
It's a 2.8 bug and it's already been reported.
