when I summon a falling block with more falling blocks riding it, the top blocks break

 on 21w06a the only half the blocks break

 this used to work

command:

/summon minecraft:falling_block ~ ~30 ~ {BlockState:{Name:command_block},Time:1,TileEntityData:{Command:"/fill ~12 ~ ~12 ~-12 ~ ~-12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~12 ~ ~12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~10 ~ ~10 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~8 ~ ~8 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~6 ~ ~6 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~4 ~ ~4 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~2 ~ ~2 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~0 ~ ~0 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-2 ~-2 ~-2 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-4 ~-4 ~-4 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-6 ~-6 ~-6 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-8 ~-8 ~-8 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-10 ~-10 ~-10 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-12 ~-12 ~-12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-12 ~-13 ~12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-10 ~-13 ~10 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-8 ~-13 ~8 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-6 ~-13 ~6 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-4 ~-13 ~4 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~-2 ~-13 ~2 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~2 ~-14 ~-2 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~4 ~-16 ~-4 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~6 ~-18 ~-6 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~8 ~-20 ~-8 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~10 ~-22 ~-10 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/setblock ~12 ~-24 ~-12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~12 ~-25 ~-12 ~12 ~-25 ~12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~10 ~-25 ~-10 ~10 ~-25 ~10 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~8 ~-25 ~-8 ~8 ~-25 ~8 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~6 ~-25 ~-6 ~6 ~-25 ~6 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~4 ~-25 ~-4 ~4 ~-25 ~4 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~2 ~-25 ~-2 ~2 ~-25 ~2 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~12 ~-31 ~-12 ~-12 ~-31 ~-12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~10 ~-31 ~-10 ~-10 ~-31 ~-10 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~8 ~-31 ~-8 ~-8 ~-31 ~-8 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~6 ~-31 ~-6 ~-6 ~-31 ~-6 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~4 ~-31 ~-4 ~-4 ~-31 ~-4 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~2 ~-31 ~-2 ~-2 ~-31 ~-2 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~12 ~-37 ~12 ~-12 ~-37 ~12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~10 ~-37 ~10 ~-10 ~-37 ~10 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~8 ~-37 ~8 ~-8 ~-37 ~8 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~6 ~-37 ~6 ~-6 ~-37 ~6 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~4 ~-37 ~4 ~-4 ~-37 ~4 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~2 ~-37 ~2 ~-2 ~-37 ~2 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~-12 ~-43 ~-12 ~-12 ~-43 ~12 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~-10 ~-43 ~-10 ~-10 ~-43 ~10 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~-8 ~-43 ~-8 ~-8 ~-43 ~8 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~-6 ~-43 ~-6 ~-6 ~-43 ~6 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~-4 ~-43 ~-4 ~-4 ~-43 ~4 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~-2 ~-43 ~-2 ~-2 ~-43 ~2 obsidian"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:command_block},TileEntityData:{Command:"/fill ~ ~ ~1 ~ ~-50 ~1 redstone_block"},Passengers:[{id:falling_block,Time:1,BlockState:{Name:redstone_block},Passengers:{id:falling_block,Time:1,BlockState:\{Name:command_block},TileEntityData:{Command:"/fill ~ ~1 ~1 ~ ~-51 ~ air"},Passengers:[\\\\{id:falling_block,Time:1,BlockState:{Name:redstone_block}}}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}]}