[MC-143894] Falling blocks can land on blocks they're not supposed to

Credit to _MethodZz_ for finding this bug.

The bug

When a falling block slides over a fence or cobblestone wall, it can land on blocks it is not supposed to.

Steps to reproduce

Build the setup in

[media]

Place a sand block under the observer
→ Notice the sand will land on top of the torch

Furthermore, if there is no torch, the sand will just drop as an item.

Linked issues

relates to 2

MC-165588 Falling blocks still convert to a block on a boat when there is a non-solid block underneath Open

MC-90523 falling_block entity floating on fences/walls Resolved

Attachments

Comments 16

numeritos 2020-06-06T22:14:04Z

Affects 1.16 pre2

migrated 2020-06-18T08:59:06Z

Confirmed in 1.16 Pre-release 8.

pulpetti 2020-07-30T21:10:36Z

Affects 1.16.2 Pre-1

pulpetti 2020-07-30T21:19:04Z

Affects 1.16.1

migrated 2020-08-05T11:34:40Z

This ticket in progress ~500 days

6 more comments

Avoma 2021-03-20T13:27:26Z

Can confirm in 21w11a. Video attached.

Avoma 2021-04-29T08:47:46Z

Can confirm in 21w17a.

ampolive 2021-07-02T15:40:05Z

Can confirm in 1.17.1 Release Candidate 1.

ampolive 2021-07-31T19:43:22Z

Attached a video with an alternate setup based on MC-183171, if ever the first one stops working for some reason.

Mr.99 2026-10-08T01:51:41Z

Well that’s strange; I’ve noticed similar behavior when placing torches under gravel columns too quickly. Observe in this setup:

I’m not sure if it’s the same issue or simply related, but it can be an annoyance when mining nonetheless. I suppose it has to do with the action of placing the torch occurring before the first tick in which the gravel is allowed to convert to an entity and fall, but I could be wrong.

For redundancy, I’ve also tested the featured contraption in the original ticket, and yes it appears to still work in 26.4 snapshot 3.

I must admit, it’s quite baffling. Noting its age and quirks, I doubt this bug will be easy to fix.