MoveIt collision checking: when is contact stored vs. not stored [closed]

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(ROS version is Melodic)

I'm using PlanningScene::checkCollision() to check for collisions, and noticed that when there are multiple collisions -- as in more than 1 pair of colliding objects -- not all contacts are stored in CollisionResult.contacts (struct reference).

I see log messages like (note the not stored in the third log message):

Found 1 contacts between 'object_0' (type 'Object') and 'link_1' (type 'Robot link'), which constitute a collision. 1 contacts will be stored

Collision checking is considered complete (collision was found and 1 contacts are stored)

Found a contact between 'object_5' (type 'Object') and 'link_7' (type 'Robot link'), which constitutes a collision. Contact information is not stored.

Collision checking is considered complete (collision was found and 1 contacts are stored)

What actually determines which contacts get stored and which ones don't?

When I unpack CollisionResult.contacts, it only has information on the contact that was stored and is missing the one that wasn't stored (which is in agreement with the logs). checkCollision() has a few overloads and the one I call is:

PlanningScene::checkCollision(const collision_detection::CollisionRequest& req, collision_detection::CollisionResult& res, const robot_state::RobotState& robot_state)

CollisionRequest's contacts, distance, cost, and verbose are all set to true.

For my use-case I need all contacts because I'm reasoning a bunch of stuff off of that.