I need to test collisions in SW2016 between various parts of a large assembly that contains many smaller assemblies within it. I encountered a slightly confusing issue. In this image below:

The foot and the motor make up one sub-assembly, along with another sub-assembly that makes up the shin part. I checked "All components", and the foot part and the shin part are clearly colliding in this image, however, SolidWorks did not detect it for some reason. 

Any help would be very much appreciated.

Thank you very much,