Circular references are the termites of the CAD world. You might not know they are there, they might not cause any real damage, or your house could fall on your head.
Your first clue that you have a circular reference is that change you make don’t affect your models as you think they should or you see terrible performance in some assemblies but other assemblies seem to be just fine. The AssemblyXpert is supposed to help you find them, but it didn’t find issue with either of the two assemblies in the quiz -so apparently it has some weaknesses. (I do have an SPR for these two, so there is hope for the future.)
Without the AssemblyXpert, you are pretty much left to manually find the problem. I typically suppress every part but the first fixed part, then unsupress each part one at a time keeping track of every mate and external reference as I go. Move the parts (sometimes temporarily suppressing mates) check your design intent…is everything working as it should? Then, if you are lucky, when you get to the part that contains/or is causing the circular references you’ll notice things aren’t quite right -fix the issue and then hope you are done. Else start the process over again!
Debugging circular references is a skill, and you will get better at finding them with practice.
Not a very rosy picture is it? Nope. That is why an ounce of prevention goes a long way which brings me to my favorite topic “Best Practices”! …