Given enchanted items are not stacking correctly

How to reproduce:

1- Give you more than a stack of stackable enchanted items (For example, 100 enchanted grass)

2- Remove a few items from the "smaller stack" and put them in their own stack (let's call them foreign items)

3- Take the smaller stack of item, exchange them with the 64 item stack

4- Take back the small stack

5- The items can't stack up with foreign items (Even when dropped or when absorbed by a hopper)