When i checked out the new snapshot on my creative world, i notice the next thing.
trapdoor gets a fake signal from redstone when breaked/placed on barrier on it.

And this is how i found and to reproduce it:
1. Put a barrier block on the ground (Desert flat world)
2. Place a trapdoor on the top edge of the side of the barrier (like so: http://prntscr.com/2o162v or pic-1)
3. close it so it will cover the whole size (like so: http://prntscr.com/2o16ob or pic-2)
4. Place redstone dust on the top of the barrier and the trapdoor will open back to its orginal placement. (Final output: http://prntscr.com/2o17oj or pic-3)

(Same thing if you place the redstone dust before, and break it)
The links are screenshots which was filmed with the known fast upload screenshot software named Lightshot