I broke off 5 studs on my Subaru Impreza over a two year period. Lug-nuts were torqued to spec with a torque wrench. Never ever had an issue with any previous cars.
Every single one broke when removing the wheel. The lug-nut would loosen slightly, then bind up on the stud and seize. When forced, the stud would snap.
I was told the cause was thread galling ( sometimes called cold welding ), made worse by Subaru's choice of a finer thread pitch for the studs, and low quality OE stainless lug nuts. I had never heard of that before, but was advised to put a VERY light dab of anti-seize on the threads only. Over 7 years and dozens of wheel swaps, I haven't had a problem since ...