I'd decided to remove the FSA Tempo square-taper crankset of my 1-year-old road bike to measure & replace its bottom bracket as it's clunking and has little lateral play. The non-drive side crank arm was stripped when I tried removing it with a crank puller, at which I immediately stopped and also gave up removing the drive-side crank to avoid risking further damage.
(Crank Puller)
What could've gone wrong? I first threaded the tool by hand without cross-threading and tightened using a wrench to engage the threads fully into the arm.
Edit: Is it just that the 3-piece crankset is badly designed that there's a high-risk of stripping aluminium crank arms?