PX4/avoidance global planner does not perform well

Hi, I tried global planner with stereo camera but the algorithm does not perform very well. I have the following questions

  1. When using default simple_obscale.world, it often tells me that the goal I choose is of high risk. Then it abandons my goal point and chooses another goal which maybe far from my goal. So what is the relationship between my goal and the new goal it choose?

  2. I create a totally empty world. But when drone plans global path in it, the path is not very smooth. Often the path shakes largely. So since there is no obstacle at all, why the path it plans shakes?

  3. I tried boxes1.world. The drone is on one side of the box and my goal is on the other side. But it tells me that it can’t find a suitable path. It is said that the planner is based on A* algorithm, why it can’t find a proper path with such a simple world?

I have search on the internet but there are not many topics about the global planner. So would you please answer my questions? Thank you very much! By the way, the local planner performs quite well!