sticky piston duplicate bug

Sticky piston duplicate bug:
I was building a enderman farm with slime blocks.
When i came back the slime blocks doubled and the redstone stuck.
Sticky piston will sometime duplicate blocks when pulling back.
The sticky piston will the block but it will refresh a new block at the place that the block was

Steps:
1.build a sticky piston.
2.build a redstone clock(or anything you can activate the piston).
3.stay away(50~75 blocks). and come back.
4.when come back. a new block(i only tested slime block)will show up.

please fix this bug quick.