The bug

In Beta 1.7.2, the moving piston block was made targetable, and right clicking on it would result in it disappearing. This was implemented to fix an issue in Beta 1.7 and Beta 1.7_01 regarding worlds repeatedly crashing due to early issues with pistons, allowing players to remove these glitched blocks and play worlds as normal: https://twitter.com/jeb_/status/86692109700186114

However, snapshot 14w32a removed the ability to target the moving piston block. As a result, if a world was loaded in Beta 1.7 or 1.7_01, crashed, and then the same world was loaded in 1.8 or newer, affected pistons will fail to work due to the invisible moving piston block in front of them which cannot be removed easily.

How to reproduce

Attached to this ticket is a world from Beta 1.7_01 in which the crash was triggered. It can be upgraded into subsequent versions to observe the effects. Note that for the latest version (1.19.3), it must first be loaded in 1.2 or later to convert it into a readable format.

In versions Beta 1.7.2 up to 14w31a, the moving piston block has a visible hitbox. Right clicking on the block removes it from the world.

From 14w32a onwards, the block cannot be targeted. However, it is still there, since attempting to power the piston will result in it not extending.

Expected results

The moving piston block would still be targetable, and right clicking would remove it.

Actual results

The moving piston block, while present, cannot be targeted and therefore cannot be removed at all.