I've also just noticed that the glazing bars, where they attach to the construction adjoining the roof don't have much overlap. There's going to be quite a weight pressing down on a relatively small cross section of glazing bar. For comparison, look how much overlap there is above the garden end. I also note that whatever it is that attaches to the bottoms of the glazing bars is short. I would have expected it to extend up to the roof bar section and form a flush edge with it. It looks more and more to me that somebody got the dimensions of the roof wrong and have cut the glazing bars as well as the glass short.