Hi, I have had this a few times now. The server just freezes or crashes or I loose connection to the server whenever there is a planet slam with units leaving orbit. If there are no units leaving the planet is works fine. Even play a lot of games with multiple planets getting slammed, no problem then. Only happens when there are units leaving orbit.
When a unit moves from one planet to another it travels in a series of elliptical orbits, treating one body at a time as it's primary gravity well. In order to ensure that the transition from one orbit to another occurs in a sane location (like outside of the orbital layer / outside of the sun) there are conditions enforced regarding the minimum spacing between two bodies. A planet that was too close to another planet (like an asteroid on final approach) violated these conditions and when the unit tried to move away from the planet the math broke, creating an infinite loop of trying to calculate where to go next. This manifested as a server freeze.
Aaaaaaaaand, posts like that are why I genuinely like this place. Ask for a technical explanation, get one, no strings attached. I'd just set the strings on fire anyhow. Treeeeeeeeees, burn for me!