During the final stretch of Lucent Citadel when the group is carrying the Arcane Knot back to the entrance, I have seen multiple copies of the Arcane Knot appear. I have seen as many as 3 copies of the Arcane Knot active at once. Once these copies appear each copy must be carried by a different group member and then constantly picked up by a different group member when their respective timers run out. If any of the multiple copies of the Arcane Knot are not being carried that Knot will begin dealing ramping damage to the group. With 3 active Knots the debuff applied to Knot carriers means that very few players, if any, are able to pick up these Knots when their timer expires.

In most cases, the duplication appears to occur after a player picks up the Arcane Knot and then dies shortly afterward.

I have heard from several people that this bug was also encountered and reported on the PTS, but I cannot find any mention of this bug in the Known Issues section of any of the PTS or Live patch notes.