Pistons moving while extending can delete blocks and/or move blocks sideways

Thanks for the extra information. If you wanted to include a test world showing these scenarios it would be helpful.

I was making a dedicated world and found that adding signs changed its behavior, so an instructional book will have to do.

Further Testing

Can break: (assume "no drop" unless stated otherwise)

• Bedrock

• Extended piston arms (piston base will turn into drop)

• Extended pistons

• Diamonds

• Trapdoors

• Doors (upper half: drop item, lower half: no drop)

• 2-tall flowers

• Beds

• Item frames w/ items

• Jukebox (drops music disk only, stops playing)

• Chest (pushes forward, then drops only its contents)

• Mob heads (drops as item)

• Monster eggs (no silverfish, I did change the difficulty)

• Dragon egg

• Torches

• Hoppers (drops contents only)

• Flower pots (drops flower only)

• Growing Netherwart

• Growing crops

• Signs

• Banners (lower half, ground mounted only)

• Pressure plates

• Slime blocks

• Rails

• Glass panes

• Ladders

• Shulker boxes

• Droppers (drops contents only)

• Redstone blocks

• Terracotta

• Glazed terracotta

• Note blocks

• Mob Spawners

• Stone walls

• Packed ice

Moves:

• Chests (piston does not break)

• Slime blocks with or without other blocks

• Redstone blocks

• Terracotta

• Glazed terracotta

• Note blocks?

• Stone walls

• Packed ice

Deals damage to:

• Shulkers

Only breaks piston:

• Observers

Crash the game:

• Note blocks (I give up trying to figure out what's going on)

• Pistons

Transmute:

• Pistons

⚠️ Revision to the book: Glitch usually occurs within the first few cycles, causes of variation are still unknown. Piston seems to prefer moving the block when piston and/or block is on the left.

Edit: It seems even the crash caused by the note block is inconsistent as there is the only one of 5 crashes with a certain exception code and different crashes list different failing modules and only happens most of the time, when it feels like it.

All three basic behaviors confirmed for latest update

This is starting to feel like a mega-report but I have no idea how to break it up. In a recent setup with sand, I created a copy of the testing world, made two sand pillars to near build limit in front of the machine and a hole to the void for the sand to fall into after being pushed and then saved. I created a copy of that and ran the test in the copy to compare file sizes afterwards and killed all entities before saving. In game it said there was an additional 1.2MB in the copy world and after exporting there was a 25kB difference between the two worlds with no difference between them other than running the machine to remove a sand pillar and removing all entities afterwards.

This is going to be my last post for a while (I'm done with all of these stupid PE bugs). The in game file size in my previous comment might be caused by MCPE-23462, MCPE-25613, MCPE-7749, etc. Still no explanation for exported file size differences

I built a snow farm with pistons quickly destroying the snoe a snoe golem places. The pistons are connected to a fast redstone clock. When a full blocks is attached to the piston, the full block can be destroyed.

Cleaning up old tickets: This ticket has not been updated recently (~1 year+) so is being closed as Cannot Reproduce. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines.

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I have replicated the setup in 1.14.60. no blocks were broken, but the sticky piston head did appear to be inside the test blocks sometimes. I will continue testing.