Collision avoidance max tracked objects?

Background: I am working on a project where there are a number of fixed place items we would like to track for collision avoidance. I have added 10 objects to track of varying geometric complexity. The add button is now greyed out so it seems I cannot add any more objects to track. I cannot find any details about the limitations of collision avoidance and or a max number of tracked objects or object pairs.

Questions: Does anyone have any further detail about collision avoidance, the limitations and possible work arounds?

Thank you,
Steve