Oops, that bug has apparently been there since the first release, but you're the first to report it.
It seems like you picked up over 90 Mk3 factory buildings at once. It's not supposed to crash in that case, just to warn you, but it still won't work, because of limitations as to how Factorissimo2 stores the data of picked-up factory buildings.
I made a patch and I'll release it later today, but for now you can avoid the crash by placing some of your Mk3 factory buildings before you pick up new ones. In the future, try to reuse old Mk3 factory buildings before you start using fresh ones.
If you've trashed your old factory buildings (whether on purpose or by accident) you can use the /give-lost-factory-buildings command to get your factory buildings back. Note that this may give you duplicate copies of factory buildings if you didn't actually lose them, but don't worry, excess duplicates will vanish in a puff of smoke once you try to place them.
