Lord of the Tar Lake Quest

I’m having issues with the Lord of the Tar Lake quest, basically the first part of this quest is recovering the BT crystal from the special large BT, the problem is that it rains in that area but there are no BTs there, I kept circling around with the coffin and there are literally no BTs there. What should I do to spawn the BTs? I watched some videos on this quest and I’m certain mine is bugged