Tripwire hook duplication glitch.

Brief Description: 

Running over tripwires in a certain way causes them to be duplicated.

Steps to Reproduce:

1. Place a tripwire hook on the back of a trapdoor. (Shown in the attachment below).
2. Place some string next to the tripwire hook. (Shown in the attachment below).
3. Place another tripwire hook on the back of another trapdoor. (Shown in the attachment below).
4. Run over the string and you will notice the tripwire hooks have been duplicated. (You start with 2 tripwire hooks and finish with 3).

Observed Results:
The tripwire hooks duplicate.

Expected Results:
The tripwire hooks should drop off the trapdoor without duplicating.

Screenshots/Videos:
I've attached 4 images which show how to reproduce this bug.

Notes:
This works with any trap door type other than an iron trapdoor.