Pillager beasts, with pistons and leaves
How I found this bug:
[media]What lead me to believe it is a visual bug:
[media]Confirmation that it indeed is a visual bug:
[media]Through my testing, it only reappears when i fly in a certain path as shown in video.
The game doesn't think that the piston can push the beast because there are blocks in the way. The beast only moves and breaks the leaves client side.