Some blocks are destroyed immediately after being placed by a structure block.

If a structure contains a redstone dust placed on top of a dispenser, loading that structure using a structure block will cause the redstone dust to be destroyed immediately after being placed.

Redstone dust placed on other kinds of solid blocks (e.g: cut copper variants) do not have this issue, but that’s about the extent of what I have tested. There might be other other supporting blocks capable of breaking other supported blocks.

Reproduction steps:

1. Place, a structure block. On top of it, place a dispenser in any orientation. On top of it, place a redstone dust. (See screenshots.)

2. Configure the structure block to save all the blocks placed above it. (See screenshot.)

3. Place another structure block somewhere else. Make sure that there is no block above it, in the place where the dispenser would be located.

4. From the second structure block, load the previously saved structure.

Expected behaviour: The loaded structure is identical to the saved one.

Observed behaviour: The redstone dust is destroyed and dropped as an item.

Additional Information

The redstone+dispenser used above are a small part of a popular 3x3 piston door design. Because of this issue, it’s impossible to load that piston door in a working state from a structure.