https://www.gamespot.com/articles/destiny-2-exotic-weapon-disabled-by-bungie-followi/1100-6458863/

Destiny 2's new Warmind DLC and accompanying 1.2.0 update went live this week, and it apparently introduced a new way for Bungie to deal with problematic weapons. The Exotic hand cannon Rat King has been found to be bugged, and rather than deal with it as it has in the past, Bungie has outright disabled use of the weapon for the time being.