This may already be known, but here goes.
When the snathi are used in a MP game and attack and enemy ship, their scavenge ability can result in different outcomes for all of the different players. That is, I as an observer could see my friend playing snathi gain no ships from an attack, but on his end he might have gained a scout. Or vice versa, he may on his end get nothing, but on my end it will show he got an attack ship. This quickly results in a CTD for either the host or the other player