Fletcher trades 15 weakness tipped arrows for 5 normal

Expected: All fletcher trades of tipped arrows for normal arrows would be the same price, and would not multiply arrows. The normal price is you give 2 emeralds and 5 normal arrows to get 5 tipped arrows.

Observed: I recently leveled up 2 fletchers. One of them trades 5 night vision arrows for 5 regular and 2 emeralds (as expected), but the other trades 15 weakness arrows for 5 normal arrows and 2 emeralds.

Steps to reproduce: level up some fletchers.