If the craft upgrade is set to place the result into the players inventory and is shift clicked it will produce a stack of 64 in the inventory. I have managed to do this to gold and netherite ingots

To Reproduce

1. Open backpack
2. set crafting table upgrade to "Shift click result to players inventory"
3. Create an Ingot our of nuggets (ex. Gold or Netherite)
4. See error

version:1.16.5

what version of the mod are you using? there was a bug in there that used to put full stack in player's on shift click which is fixed in the last few versions

I can't recreate it in either dev environment or in modpack I am playing so I am going to assume the version where it happened was one before this issue was fixed a few versions back.