Aiming at the very bottom of a side of an upper slab/stair places slabs/stairs right-side up in multiplayer

Just place a slab of any kind on the upper side of a block many times, and you'll sometime get one that converts to being on the bottom side of a block.

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_{Description from MC-89850}

When placing top- or bottom aligned blocks like slabs and stairs server and client disagree about the alignment of placed blocks

Doesn't happen in single player (or isn't visible), but on dedicated server or Realms.

Steps to reproduce:

• Place a block with a well defined center (e.g. stone bricks) at ca. eye level
• Take a stair or slab
• Aim slightly above the center of the block
• Place block

The results:

• Client places the block at the correct top alignment
• Server overwrites the block a split second later at incorrect bottom alignment

Screenshots show before and after placement (the in-between position is quite difficult to capture)

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Code analysis by [Mojang] Panda in this comment.