I have run into a problem in iC8 when it renders a 4K scene using the Aura particle. I will get an error about some memory error message and then iC8 will crash. It is always the same frame where it gets stuck.
Fortunately, I have an iC7 scene backup for such situations. I am able to render the 4K scene without it crashing at all. I suspect I am the culprit as I made mods to the Preferences where you can limit transparencies. The first time I did this I got no video output as the number was too low. Bumping it up to the max, it was rendering until it crashed once again from a memory error.
Moving on is the best solution as I did get a 4K render out, which was my goal when dealing with problems such as this. I had originally uninstalled iC7 and CC3, but re-installed iC7 in order to get this scene done.