To complete a simple temporary repair I would use Selleys 250ml Aquadhere Exterior Adhesive and apply it with a small brush inside all the cracks. Clamp the area bringing all the fibres back together and reducing the cracks. Once the glue has dried and if there are still visible cracks, you could touch the area up with White Knight 100ml Splashes Gloss White Enamel Paint.
Once the exterior coating of the door has been penetrated by water, the damage will continue as long as it is still exposed to water. You might find replacing the unit could be an option worth considering and we offer an extensive range if you choose to do so. - MitchellMc
