I regularly use DIM and the D2 Mobile App to shuffle my gear around, make changes, and whatnot. Today, I noticed that I could select different perks to apply to my guns. Note, these guns did not originally offer double perks per slot. I do not know if this was an intended change, but it looks like the API accepts these changes. For example: selecting a different perk in DIM will remove the original but accept the new selection. Checking the same gun in the Destiny Mobile App shows the new perk as the current/active perk on the gun. My suggestion, if this is not an intended allowance given to players, is to disable the API until the bug can be fixed.