This is one of the problems I had with Flow frames, but in my case nothing was visible from the outside - one of the vertical blades broke and created a gap for the bees. I had to dismantle the frame to find it.
From your photo I can see another problem, which again I have on both of my Flow supers. There is a gap between the bottom of the Flow frames, and the aluminium strip. Make sure that the frames are pushed back against the back of the box (they look like they are), if that gap remains, it is another defect. My bees weren’t coming out through those gaps last season, but they are this season, looks like the gaps got a bit bigger somehow.