The Kagrenac’s Hope set / Battle Resurrection is bugged and has been confirmed by ZOS.
I also experienced this “bug” just after I had crafted my Vr16 Kagrenac’s set and put it on. It seems to be a common link between all of us who have had the issue. We went from VR14 old gear to our new VR16 crafted Kagrenac’s and could tell something was not right….
I believe you may have nailed it, when we change gear it does not apply the [Battle Spirit] buff. Ever since coming across this thread I have swapped gear in an effort to test and because I was paranoid. Little did I know that is most likely what is causing it. The only counter to your theory is that when I crafted my gear in Bangkorai I put the gear on and then zoned into IC, so it may not be when you zone in.