I posted about this in the GitHub bug section in the bug about Fitness throwing an error when you first load a legacy build (I erroneously thought they were related, but they are not). This is happening with the Blaster Tactical Arrow set. To duplicate, start a Blaster build in Pines, select your T1 Primary and secondary, then save and re-load in MR. You will see Electrified Net Arrow in yellow, and it is unselctable, and Raptor Pack is in place of your T1 Secondary. I posed screen shots over there as well.
May be happening for other sets, but that's the only place I have seen it. My testing, however, is far from exhaustive.