I’m glad to hear that you’ve narrowed it down. Unfortunately I’m not getting the same results. Have you tried using the cubemaps included in the engine content or is this occurring with your own custom ones? You can find the engine content ones by selecting the View Options icon at the bottom right of the Content Browser and selecting “Show Engine Content”.
If it does only happen with your cubemaps, would it be possible for you to send those assets or the small project you created that is experiencing this freezing behavior?