problem mating 2013 vex parts in Inventor 2015

I am some difficulty mating the 3d parts from the Inventor 2013 Vex KOP Imperial from Appendix 9 in the Vex curriculum. I am using Inventor 2015. Problem: I am trying to constrain a bearing flat to c-channel. the imates do not line up with the bearing flat over the square hole.
Test: I tried mating the bearing flat from the KOP in Unit 4 section for building the clawbot and it works perfectly. the bearing flat round hole is perfectly aligned with the square hole of the c-channel.

Any ideas on what might be causing this?