Falling Sand Stuck On Fence

Sand on Fence or Closed Fence Gate is stuck. and the sand doesn't despawn. it also jumps slightly up every 3-4 seconds.

HOW TO REPRODUCE:

1.Put a fence or closed fence gate
2.place sand 1 block above it (not directly on top of the fence)

WHAT I EXPECTED TO HAPPEN WAS:

the sand would drop as a item

WHAT HAPPENED:
the sand is stuck