This issue is basic and simple: when you use the pickerang (and probaly the flamerang if it uses the same code) the items it picks up are given NBT data for some reason and because of this, items are not stacking properly (because items with Diffrent DATA will not stack)

the sollution: if its possable, try to make sure that the items that are collected by the pickerang dont add NBT data to the items it collects

Steps to Reproduce:

Let us use Logs for this example,

1 aquire 10 logs of the same type form the creative inventory

2 toss half of the 10 logs (5) onto the ground and distance yourself from them

3 using the pickerang, toss at the items and let them collect

4 Hopefuly get the result of the items not stacking

5 using f3, enable advanced tooltips and hover over the 2 items that refuse to stack and noticed that one will have 2 nbt tags, that one being what the pickerang picked up

This issue has been made invalidated, sorry for the waste of time