What I expected to happen was:
The piston or sticky piston to extend the block in its normal state.
What actually happened was:
See here: http://gfycat.com/SameRadiantBlackbird
The piston or sticky piston will throw blocks of meta data 6,7,and 14 into an invalid block state ultimately causing the following and recurring log errors attached on smp.
It appears for a split second the meta data changes back to 0 from 6,14, or 7. Blocks will exhibit behavior as the following gif I recorded. It's quite clear that red and pink wool will change to white wool for a second.
Complex machines such as wither skeleton farms, crusher systems, enderfarms, and witchfarms can cause servers to crash or clients if blocks of meta data values 6,7,14 are used.
How you reproduce this:
Go onto to a server whilst viewing the console or enter a minecraft world and push any block from the list below with a piston:
The following list may be missing a few blocks but there's a pattern with meta data values
Red Carpet (14)
Pink Carpet (6)
Red Stained Glass Panes (14)
Pink Stained Glass Panes (6)
Red Stained Glass (14)
Pink Stained Glass (6)
Grey Stained Glass (7)
Polished Andesite (6)
Red Stained Clay (14)
Pink Stained Clay (6)
Red wool (14)
Pink wool (6)
Nether brick half slab (6)
Gray stained clay (7)
Gray wool (7)
Quartz half slab (7)
Birch wood (6)
Environment
Operating System
Windows 8 64-bit
CPU
Intel Core i5 3427U @ 1.80GHz 53 °C
Ivy Bridge 22nm Technology
RAM
8.00GB Single-Channel DDR3 @ 798MHz (11-11-11-28)
Motherboard
LENOVO S500 (U3E1) 53 °C
Graphics
Generic PnP Monitor (1366x768@60Hz)
Intel (Lenovo)
2047MB NVIDIA GeForce GT 720M (Lenovo) 44 °C
Hard Drives
466GB Seagate ST500LX005-1CW162 (SATA) 36 °C
Optical Drives
No optical disk drives detected
Audio
Logitech G35 Headset
Linked issues
is duplicated by 10
Attachments
Comments 10
Data value for all of those blocks were removed. MC-57470
Nice to see bugs related however not a duplicate. Pistons are at fault for moving into those data values.
Error log of server.