In the 14w08a FallingSand entities do not render properly. They will only render after hitting the ground.
This also affects FallingSand riding other entities.
Linked issues
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Noah, How could I take a screenshot if it does not render? It only renders when it lands. Don't matter the Time, the TileID, the Motion, if it is riding an entity or not.
Cannot confirm. Falling sand renders perfectly fine. Is there any special steps to reproduce this with, and do you have any screenshots?