When you say "but since JFBConnect v4.3 I've noticed the problem", do you know if you looked at this area of your site when you were using v4.2? Many times, users upgrade and they simply notice issues that existed before, but they never saw. It's ok if you did (or didn't notice) before, it just helps us narrow down if it's really a v4.3 thing or something that has just been going on a while. In general, we really didn't touch any code with the faces for the Fan module or anything else in v4.3, and we simply call Facebook's code to have them show the faces anyways.
While we definitely had an issue with the Like button that was our fault, the 'interior' of the modules, we have little control over. Definitely confused as to what's happening, but will continue trying to help however we can.
I have found some bugs logged into Facebook that seem to describe the issue (along with settings that cause the problem). You may want to look through these to see if it's the same bug(s) your affected by:
developers.facebook.com/bugs/193583344100320
developers.facebook.com/bugs/312382875517810
From that last one, Facebook admits they can reproduce the problem, so I'm pretty sure this is a Facebook issue and not something we can fix.
Hope that helps,
Alex