The issue it falling sand inside a spawner crashes your game and rids your map useless without third party programs.

On my redstone ready test world I was working with a custom spawner to create a FallingSand Fire spawner, the world crashed and I restarted a new one. After assuming the animation wouldn't render due to the new update, I tried A FallingSand Web spawner. Then this crashed my next world, finally I tested a regular command for a FallingSand Spawner, once more this crashed my game.

Recreate with a single command:
/setblock ~ ~ ~ Minecraft:mob_spawner 0 replace {EntityId:FallingSand,SpawnData:

}