The hinge bar is sealed with non-setting mastic and slowly this has hardened and is pulled off by the weight of the window, as the number of screws is IMO too small , then the water pours both down the back of the hinge and into the screw holes and into the inner wooden frame which supports the window , rotting it ,The Xplores are well known for this. IMO you should remove the window off the hinge ( see below) , then the hinge bar as Birdman101 suggests and when refitting , fit extra screws ( 3.5mm x 18mm csk stainless) , remember to countersink the new holes in the hinge bar. You should check out the front window as well. I have, over the last eighteen months completely replaced the front framing and front shelf on three Eddlis Xplores!( and on one also replaced the complete rear wall) . To inspect the wooden framing, working from the inside you can peel back the rubber window seal to see if it's damp ( the outer lip of the rubber seal has non-setting mastic on it which won't allow it to be lifted. The large front window can be carefully removed by unscrewing the two stays from the frame and rotating upwards( two people) to release from the hinge ( there are three little plastic inserts screwed to the hinge which need to be removed to help release the window from the hinge , If its been leaking for a while then the wooden frame will be soft You may notice the screws in the side holding the stay bracket don't unscrew properly(just turn) and this a sure sign the wooden frame is rotted and may need replacing , Good luck and I hope you have caught it in time.
