»Blocks despawning in SKyblock

I use sand as part of my automatic sugarcane farm and every now and then some of the sand despawns, I just want to know why and how i can fix this? Below link will take you to a screenshot of this.
http://imgur.com/a/n8lRA

 

Entity clear plugins will remove falling sand if it happens to clear at the time the piston lowers. Instead, I've found that a sticky piston and wood plank works (since 1.9?) for this kind of farm in place of the piston and sand.

 

Thanks for the answer and also how do you use stick pistons and wood planks instead?

 

The upward facing piston that the sand sits on can be replaced with a sticky piston and the sand can be replaced with a wood plank (or probably other block, wood was what I tested and it worked).

If you want to see it, you can go to my warp in skygrid and jump down to the taller sugar cane farm.

The shorter one uses observer instead, much better overall.

 

Thanks for the help man