I found this bug on the latest release, 1.21 and it's really weird. Whenever I spam place sticky pistons on a redstone block making them face two different directions, one of the pistons glitches and disappears, but it's head is still there and the head becomes unbreakable and the only way to fix it is to place a piston again facing the same way as the floating head which makes the head reattach itself to the new piston and after breaking that placed piston the head also breaks. It's not a fluke, I tried it multiple times and I could do it every time.