Stacking Blocks Not Working

hey so im working on this mod for a server and i have a mini version of a carved pumpkin. your able to stack them if you have multiple however when i try it in game it immediately stacks to the triple stacked version skipping the double stacked version. I'm using the when block right clicked trigger inside the block. and if your wondering, no adding a cooldown to the item stack does not work as its happening all in one tick before the next can update.

thank you