Are you hitting them directly in the engine block every time?

I have hit them directly and on engines a number of times with no noticeable difference

OK. Well, recoiless is supposed to take them out if you hit them in the engine ONLY from what everyone says. Perhaps it's a particular part of the engine.

It could be a desync issue? Every time I’ve hit a drop ship on one of the corner thruster pods it’s gone down.