I've have noticed issues (on this forum) with mating issues, in regards to being over-defined, etc.  However, I am experiencing an issue with a basic "coincident" mating relationship, where when I originally select the mating features, the mates are fine.  It's when I save and/or re-open the assembly that the mating takes place with a different (unselected surface).

I select the two mating surfaces between the bronze piece and the black piece.  Again, after "accepting" the relationship, the mates are fine.

It isn't until I save and/or re-open the file that it mates incorrectly.This is what it does (looks like) everytime, after I save and/or re-open file....

The proper mating should look like this,.....

ANY ADVICE??

Thank you!!