After importing my WSE string into the WowSims website, I noticed that one of my reforges was incorrect.

I have reforged this item's Expertise into Haste.

Export String: {"id":59223,"gems":[52212],"reforging":167,"enchant":3222}
Note the reforge ID of 167 - this ID is for Mastery into Haste

I believe the issue lies in the GetItemCurrentStats function. In this case, the function has returned a value of '10' for mastery - matching the item's socket bonus. May need some logic to avoid parsing socket bonuses, similar to the current logic that it's using to avoid parsing enchants.