Tripwire broken?

I wanted to make a slime block machine, but in the latest snapshot... tripwire / string is buggy.

First I placed two blocks just underneath where the tripwire should go. It connected and worked all like a charm. Yet, when I broke the blocks where the tripwire was place on, the string broke!

But when I placed string upon string and reached the heights of the hooks, the string didn't want to connect.

I also have a fresh install of Minecraft.

Update: I was able to get it working with a 1-block gap. But a 2 block gap, nope :/

Edit: Like Simon said, if I remove the blocks underneath the hooks, the tripwire works like a charm. BUT, when I placed a block underneath the hook at the left hand side, the tripwire broke. I heard a sound of an arrow hitting something. That arrow sound you mostly hear in jungle temples.

So, using the F3 menu, the hook was facing north.

When I tried to place tripwire in the different direction, (hooks facing east and west) the same bug occurs when the hook is facing east.