Further tests show that the crashes happen only if I try to render from a view where the transparent ring overlaps the Sun. I can't figure out why though. It's the only angle that crashes the scene even with the "Allocate on Heap".
Also, the RAM isn't even used up halfway when the crash happens.

I can make it crash only from that angle and this is what happens when I render halfway.

I'll try to export stuff separately, maybe the importing had something to do with the problems.
Or the textures.
The entire file has reached 30 mb.