I figured it out in the end. It was the ‘Screen Space Reflections’ that were causes the visual bugs. I set the intensity to 0 and that has eradicated the problem.
Still, it’s strange that this hasn’t shown up in PIE.
StephaBon, does that sound like something that could be effected by scalability settings you mention? I will check over those anyway, but the problem is otherwise, seemingly, resolved.
Thank you!