if you use the items ID code instead of the name, it will fix the bug. for ex. when i did /shop set sell Lead 500, it set the sell price of oak leaves to 500. it did this countless times to other items. I looked up the ID for the Lead which is 420. I then put the ID code in place of the name, for ex. /shop set sell 420 500. it therefore didn't bug out and listed my lead in my store as 500.