Unidentified error?

I observed with a map that is exported from a Java server (Spigot 1.8) get the following error
[02:18:20] [Server thread/CRITICAL]: UnexpectedValueException: "Invalid pocketmine\entity\object\FallingBlock entity: block ID is 0 or missing" (EXCEPTION) in "pmsrc/src/pocketmine/entity/object/FallingBlock" at line 69

Also the world generation is very slow, which causes lag in the players. Is there any solution?

 

I want to add more. This error appears constantly when a chunk is loaded.

 

I think that have FallSand Remove That For fix Error I hope that fix