Contraption making piston ghost blocks

Are these "ghost" pistons or actual pistons? That is to say, when you place a block directly next to these pistons do they disappear? And just to confirm, did this occur in singleplayer?

 they aren't ghost blocks, and it did occur in singleplayer and also later i did the same thing on multiplayer

I could recreate this in 20w09a, however, for me it's ghost blocks (can walk on them, but as soon as I rightclick them or re-enter the world, they were gone).

I recorded it, just in case it's needed.

@unknown You resolved this bugpost as Duplicate of MC-54026, however, said bugpost is resolved as "Cannot Reproduce" - should that old bugpost be now reopened instead?

@unknown Reproduction steps: Load structure from

Activate Observer, as shown here

It may take sometime until ghostblocks are created, but there definitely will be.

Could a moderator please confirm me that this bugpost will be reviewed again by a Dev, or maybe Mr. Siverman specifically?

I can reproduce the fake duplication / ghostblocks in current snapshot 20w09a after all, and I provided also a structure block file, with which this happening can be confirmed.

On a side note: Unfortunately, I can't chose something like a Mojira mod role at "Viewable by All Users", so I have to ping everyone by messaging publicly.
I would find it great if it would be possible to do so, annotations solely towards Mojira mods and higher; for some bugposts, it could be good if not the whole public could see some remarks, and not everyone watching a bugpost would get pinged.

Thanks for the repro @unknown. This will indeed be looked at.

@unknown Thank you 💙

Can confirm for 20w13a, am on mobile, thus can't test right now for b-snap.
Demo of ghostpistons here https://www.youtube.com/watch?v=DplyWcJj258

Confirmed for 20w14a.

Confirmed for 20w17a.

In case the OP doesn't mind, I'm willing to take over this bugpost.

Can't confirm in 20w18a.

Can confirm for 20w18a.

Thanks Meri, I wasn't able to reproduce on server as before.

No problem Johnibur, it didn't create any ghostblocks for me at first, too, only 2 times 1 ghostpiston directly when I logged in, or relogged; after that it didn't create any ghostpistons for at least 10 minutes. After I relogged 3 times, they were created like crazy.
I usually test in SSP, but good call, I'll test this from now on on SMP as well.

Confirmed for 1.16 pre-5.

Confirmed for 1.16.1, requesting ticket ownership.

Confirmed for 1.16.2 pre-1.

this bug happen when a blockevent try to push a moving block in the 1st or 2nd tick

here is some setup that make it more clear,trying to push at the 2nd tick:

The reason is in PistonMovingBlockEntity.java (mojang mappings)

if the client dont receive a packet to turn the moving block back into a block,the block entity progress of the moving block will still increase clientside but the animation stop and a counter: "deathTicks" will increase

when it go over 5,the moving block block turn into a block clientside and remove the blockentity,so the block can be pushed clientside and create a ghost block

this can happen if there is a server side lagspike and the client can execute about 7~8 ticks before the next server tick

a solution could be raising that "deathTicks" limit, or removing it (I dont know the the effects, it could leave some glitched extending pistons when players have a bad internet conection, EDIT:bad idea, moved ghost blocks will just get stuck,they are already stuck for 6 tick after moving)

a solution could be comparing the tick of creation with the current tick because it's synced with the server tick and wont be affected by how many times the client tick

Confirmed in 1.21.3

I am unable to reproduce this issue, can you confirm that you are still able to reproduce this issue on the latest version?