Safeguard/Mayhem bug

Did a search and the only threads I could find on this were from about this time last year, so apparently this hasn't been fixed yet.

The bug being the hero or villain in the bank disappears. That is, the character model disappears, leaving only the visual effects of their active powers visible (or in the case of the villain in a safeguard, a sack of money floating in the air in the middle of the power effects), leaving the mob untargetable/unhittable.

Previous threads have connected it to the mob being near an elevator, i.e. just came out of it, and that was the case when I ran into this during a mayhem mission. I just finished a safeguard, and this time I was just inside the bank entrance where I'd been fighting the guard mobs in the lobby. The villain, Shock Treatment, appeared, and I got her down to about 5% health, and then she vanished, leaving only the bag of money and her electric armor showing.

So I made a beeline for the escape point (an Arachnos flyer in this case), and pretty soon she appeared ... still as just a floating bag of money and an electrical field.

This isn't happening every time; I've successfully completed several of these missions. It's just every now and then...