OK, Jason, you've convinced me - it isn't the fitting, it's the design of the door itself.
(He pointed out that there is a thin seal that protrudes from the bottom of the doors). This prevents water splashing up and into the room. Where the design is poor is that the door does not have a very positive location point when it is in the shut position and it's easy to push it out into the room slightly. Thus the water runs down the glass and onto the floor!
As you see, the door folds in...
and it's easy to not locate it properly in the middle where it is supposed to be - on the frame.
Also, if you push it out when you exit the shower, all the water runs down the glass and onto the floor!