Thanks xenlock, that’s an insightful investigation.
Yes, I’m using strictly blueprints, so I’m basically stuck, until the devs get to my bug report (if ever).
I did try several hacks, everything from trying to force a HISM update in [Event Begin Play] to [DoOnce] in the [Event Tick]. As you’ve identified, the problem is at code-level so probably nothing I do in a blueprint will overcome it. 
Did you post a bug report or just stuck with your code workaround?