Falling blocks break when landing on mud. I suspect this is due to entities sinking slighty.
Steps to recreate:
Place a mud block, any full block on top and a gravity block (like sand) on top
Break the full block
The sand should start a freefall on the mud
Expected results:
The sand should stop falling once reaching on top of the mud
Result:
The sand breaks instead
This bug occurred to me when I was exploring a mangrove biome and a beach biome combo. I hope this gets fixed.
Mud is not a full block, therefore falling blocks break on it.
Freefalling blocks are not a thing in Java Edition, it is therefore inteded behavior.
If you believe this should be changed feel free to post your suggestion on the feedback forum