After some extensive testing, I have found that the "Achievements" tab in the BuddyPress profile only works directly out of the box. If you use multiple achievement categories, not all of them will display. Here's how I think the program operates and where I think there is a problem.
How it "should" operate:
1) Admin creates multiple categories with multiple badges/awards/medals
2) User unlocks an award.
3) Upon unlocking an award, the BuddyPress "Achievements" tab is supposed to trigger so that the tab displays.
4) Clicking on that tab will show all the achievements a user has earned from all categories.
Here's some problems I noticed:
1) The trigger to display the "Achievements" tab does not seem to be all-inclusive. If I just make one category and make achievements only in that category, everything seems to work fine. The problem arises when one starts making multiple categories. This leads me to believe that the trigger to display achievements is too defined and needs to be broadened.
2) The display of achievements is also confined to only 1 category. Something in the coding needs to be expanded to include all achievements, not just one category.
I am not a programmer, so this is just my two cents. I tinker with code a bit so perhaps I'm on the right track here, but I just wanted to write this so that the plugin developers might have a better idea of where the issue is so they can adjust it.