How to recreate
1. Open a world (in beta)
2. Give allay a block
3. Kill said allay

So when you give the Allay the original block, the Allay does not drop the block after death.
Might be a bug or an intended feature

What I think should happen: The Allay drops the original block that the player gave to tell him to gather
What happens: The Allay does not drop the original block