I usually don't have a problem with Geckos, since the cockpit method seems to be fairly effective on those beasts (as long as I remember to go through and evac all the air regulators and loose cargo bits first), but late-game Mackerels just give me the fits. If I try to vent via the cockpit, I usually wind up with it pirouetting around the bay and throwing itself into the furnace. If I go the airlock route, it lurches sideways into the processor.

Or the reactor cooks off after being nudged by a bit of random space trash that I can't grab and it blows itself to flinders.

Or the winglets (exolab variant) are overlapping each other and cause it to rotate like a prop as soon as one is torn free, causing random breakage inside that usually leads to either coolant superfreezes or fuel tank splosions.

Or something bumps a battery pack and OH GOD ALL THE SPARKS AND FIRE. Even when there's no air for the fires to, y'know, burn with.

Or the crawlspace between the hull and the interior spaces is sealed off and retains pressure even after I've managed to vacuum out the rest, and when I pop the seals at the back the entire thing rockets forward at mach 8 and bounces off the hab.

--sofaspud
--you can see it dwindle into the distance for a surprisingly long time before the game tells you it's gone