bundle Dropper bug

What I expected to happen:

The Bundle and the items inside it should stay the same while the Droppers pass items back and forth.

What actually happened:

By keeping a Bundle inside the Droppers while a redstone clock is running, then opening the Dropper and right-clicking, the items inside the Bundle can be duplicated. In the attached screenshot the Bundle contains 30 diamond blocks.

Steps to reproduce:

1. Place two Droppers facing each other and connect them to a redstone clock that turns on and off rapidly, so the Droppers keep passing items back and forth (see screenshot 1).

2. Put a Bundle containing the item you want to duplicate (for example, diamond blocks) into one of the Droppers.

3. While the clock is running, open the Dropper and right-click.

4. Repeat step 3 until the duplication happens. It does not work every time, so it may take several attempts.

Frequency: Not every attempt; it can take several tries.