The bug:

I was testing the same resource pack I made that adds/tweaks sounds and textures to the game when this occurred. I placed some blocks (3 apart), 2 tripwire hooks, and some string in the middle. I got some shears then broke the string in creative mode. I saw that the tripwire didn't break and doesn't even trigger the hooks anymore. I recorded a clip to demonstrate the bug. (It may be in terrible quality because the upload limit was 10 MB.)

To reproduce:

1. Be in creative mode for best results. Survival also works but it works 100% of the time in creative.
2. Place down 2 blocks that are at least 3 blocks apart from each other.
3. Stand on the middle and face the blocks. Place a tripwire hook at each front of the blocks.
4. In the middle, place a single piece of string. You should hear a click sound.
5. Get a pair of shears and break the tripwire.
   → Observe the bug happen.

Video:

Mojang JIRA bug report 2.mp4