Hopper item duplication

I'm making a system that relies on hopper clocks. When I either exit the chunk or exit the world, the items in the hopper will duplicate sometimes.

What I expected to happen:

The items in the hoppers stay the same

What really happened:

The items would increase on a random stat of chance

Steps to reproduce:

Step 1: Create a hopper clock
Step 2: Exit the world a few times
Step 3: Check the hopper
You'll see that there might be a duplicated version of the item inside