Spiders Crash The Game When Taking Damage Through Block

I was able to make quicksand and it works perfectly the only thing i did was make it so that you can walk through the block, it has gravity, and i made a procedure so that when you're under another quick sand block it does 1 point of damage. This works perfectly with other mobs as well except for the spider the second it hits the inside of the block it crashes the game completely.