If you place a piston with a redstone block above it, powering it, and a redstone block on top of that, then break the lower redstone block, the piston will not retract.

This is not just a visual bug, as placing a block in front of the piston will cause it to retract and bring the block with it.

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I also had another issue recently where redstone did not update when unpowered but I chalked that up to being on a PaperMC server. If I can manage to recreate that, I'll update my post with that information.