Duplicated Piston Arm

The piston arm got duplicated.

What I expected to happen was...:
The bottom piston should push the top piston to the powered space and the top piston should extend. (http://imgur.com/sO5ODXY)

What actually happened was...:
The piston arm got duplicated.

Steps to Reproduce:
1. Build the mechanism shown on http://imgur.com/iusUQmW (So that the two torches emit power at the same time)
2. Switch the lever
3. This would happen: http://imgur.com/uH366bD