Yup, that's a bug with Facebook and there's nothing you can do about it. The good news is that the issue goes away as you get more Like's for your page. Basically, Facebook will always show avatars for as many rows as you have it set. If it needs to duplicate some to make it 'full', it will. Once you get more likes (>10 or so), there shouldn't be any duplicates, or it will only occur rarely.
Hope that helps explain!
Alex
Redundant FB profile pics in JFBFan module
