When for example a command block as FallingSand falls next to a block providing a redstone signal, it won't update.
Example command
/summon falling_block ~ ~2 ~ {Block:stone,Time:1,Passengers:[{id:"falling_block",Block:redstone_block,Time:1,Passengers:[{id:"falling_block",Block:command_block,TileEntityData:{Command:"say Test"},Time:1}]}]}
When you place a block next to it, it will say "Test".
Note: It appears that this only affects block entities. Here are some examples:
Affected blocks:
Dispenser
Dropper
Command block
Unaffected blocks:
Rails (Activator and golden)
Redstone lamp
Piston
Linked issues
duplicates 1
Comments 11
He means when it lands and solidifies into an actual command block, the redstone doesn't power it until you give it a block update.
Confirmed for 1.12 pre-3.
For the example command in the bugpost to work now, it should be updated to:
summon falling_block ~ ~2 ~ {Block:stone,Time:1,Passengers:[{id:"falling_block",Block:redstone_block,Time:1,Passengers:[{id:"falling_block",Block:command_block,TileEntityData:{Command:"say Test"},Time:1}]}]}
Confirmed for 1.12 pre-5.
Confirmed for 1.12 pre-7.
Confirmed for 1.12.1.
Confirmed for 1.12.2 pre-2.
Confirmed for 1.12.2 release.
Confirmed for 17w43b.
Merging with MC-51340 as it's the same cause.
Fallingsand is an entity, it doesn't conduct anything.