I play on PC with a bluetooth Xbox One controller. After dealing with big drops in framerate at seemingly random times, I eventually realized that it only occurred when the controller was resting in my lap, which meant the direct line between the controller and my PC's internal bluetooth receiver was blocked by my leg. It was 100% repeatable after that realization. I could block the direct line-of sight, the framerate would plummet from ~60fps down to the teens. I lifted the controller up to clear its view, and the framerate returned to normal. I repeated this a dozen times in various contexts-- in orbit, in the menu, on the ground, in the tower-- with identical results every time, although the starting framerate was higher in orbit and the menu than on the ground. I could also instigate the same framerate drop by standing up and walking my controller about 20-25 feet away from the PC. In summary, my framerate problems were directly tied to the strength of the bluetooth signal from my controller. I wonder if other people using bluetooth peripherals (controller, mouse, keyboard, headset, etc) might try reorienting their peripherals to have a stronger signal then a weaker signal to see if that causes similar framerate issues. I don't have this issue playing other games on my PC, only Destiny 2.