I have noted with some friends of mine, that since Gamma release planets with radius 1200 are not being able to load for people, i am talking of a system with 1 big planets and 2 moons. previous in Beta this was working fine, but for some strange reasons i don't know exactly why it happens to crash some people's game. Mostly during the Generating Planets. My guess is the new loading of systems has to do something with this performance issue, but can't say for sure. Also i have noted that when u got around 2000+ units the game goes really lagging at that point to clear out the game. I know it isn't released yet and my main point is they may be a small performance issue in the new generating system setup. Site note: Me and my friend got top line gaming computers and played since Alpha we hadn't had a lot of performance issues in Beta with this size of planets.
Same issue here, only in my case it takes around 5-10 minutes to load large planet sizes and the game crashes at seemingly random intervals when designing planets in the system manager.