There is this strange wheel-like piece consisting of two pieces snapping into each other and offering to insert both axles from both sides, as shown in the first image.
What is the purpose of this part instead of just using a straight axle? I see that the holes for the axles are twisted by 45° between the two parts, but for that purpose, a much simpler part similar to the tubes joining two axles could be designed. The only purpose I can vaguely imagine is that it's sort of a clutch limiting the torque to prevent damage.
I particularly wonder why this is used in the track roller of the Liebherr excavator (42100 set) as shown in the second image below.