Select a block.
Place the block. One, to, three times, also rotate it. Look at the cursor.
Calculate the shadows (I have used "Fast").
Now try to place the same block. The lightmap at the cursor is bugged, and this on two sides.
Apparently always opposite to the sun. You can rotate the block, the lightmap issue is always on the same sides not oriented towards the sun.
As soon as you place the block, the lightmap on the placed block is gone of course.
This effect is visible on many blocks.
And yes, before taking the above screenshot, I have cleaned the cache (using the button in the launchers P2P settings only).