Im guessing you are doing the final diamond puzzle. If you are jumping through the tunnel, try going around instead. I think sometimes when you touch the rotating panels inside the tunnel it screws around with the tether's detection. For, beasting the harpies make sure your team has as much resil as possible and use two concussive dampeners, it helps drastically. Lastly, be careful jumping on and moving over stares, that can mess with tether as well. When you have the two people connecting the diamonds on the staircase just take it slow moving up the stairs nice and easy. Ur not timed, take it slow. One last thing, don't block with a sword while tethered because it will break the link. If you make it to the boss, good luck I hope you finish. 👍😊