Grouped joints messes up collision detection

[protective1]

The grouping required for making joints seems to conflict with collision detection.

If I do the following:

1. make a joint between object A & B,
2. attach the joint to object A,
3. group the joint with object B,
   then the collision detection for object B gets broken.

In the attached file, I've have linked three boxes, and the two joints are grouped with the box in the middle. Notice that the middle box can pass through the outer two boxes (no collision detection). What am I doing wrong that prevents the middle box from having proper collision detection?

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3 objects connected by joints. collision detection for middle object is strangely broken - it can incorrectly pass through the outer objects.

[protective1]

I found out that there is a setting on each joint (as seen in the SketchyPhysics Inspector) called "ConnectedCollide" which is disabled by default. This setting must be checked for objects connected to the joint to undergo full collision checking.