The logjam occurs all the time and it's a result of the all aboard process. The passengers sitting in the forward portion of the main cabin have an inordinate effect on slowing down the boarding process. Rows 7 thru 15, or so, are always where the backups occur. Another portion of the problem is that the FA in the cabin always gets pushed back (because there is no place to work) and when the FA needs to be helping pax getting settled they are not in the area having moved further and further back to get out of the way.
I understand that TANGO is being revisited as well that possibilities exist for modifying and/or completely revamping the boarding process. Will any of these ideas reach fruition? Who knows... hopefully something changes because the current 'all aboard' is hard on pax and employees alike. It would be nice if the FA in the cabin could actually do their job but in the current system it's almost impossible.