So today the time has come to try boarding combat for the first time (hint: it's super effective compared to fighting conventionally and have enemy shoot back at you) and, according to the rules, my boarding-capable marines on a shuttle roughly 3x faster than the enemy should mean each soldier has roughly 60% chance of surviving, getting to the hull and taking part in the firefight inside. And that seemed to be the case as I looked briefly at the casualties during boarding attempt, roughly 60% of the soldiers made it...
Except one thing. During each of two attempts done with 18 formations, 6 of them vanished without a trace.
How is that possible? I haven't found anything in the rules that'd justify this sudden evaporization of entire formations.