Not much of a help, but when you get a replacement, put a piece of Gorilla tape over the hinge area to reinforce it. As for the locking tab,  you can't put Gorilla tape there as it would prevent you from opening and closing the carrier.you may be trying to cram too much hose in there. If you can't shut the door easily, then it is putting a lot of stress on both the hinge pins and locking tab. If you can find the stiff hose that you can collapse and it stays that way ( https://www.amazon.com/Camco-RhinoFLEX-Translucent-Frustration-Free-39770/dp/B01HPHR2M4 - like the Rhino Flex Hose ), then once you get it to fit, then it is not stressing the hinge pins or locking tab. Since you probably already have the elbow, you could save some money by purchasing the 10' extension hose unless you want the new elbow and storage caps. Even so, you may need to shorten it a little to fit the carrier. At least it is easy to do so with the Rhino Flex hose.

You can order a replacement door also. https://smile.amazon.com/Valterra-Sewer-Carrier-Replacement-Black/dp/B016EE4FGA/ - Valterra Sewer Hose Carrier Replacement Door . When you go to the page, there is no picture for the single door. Mouse over the "4" option and a picture will show. It is cheaper to order four individual ones than the four pack. When I had to replace one, I could not find the door alone and had to get both the door and the bracket. However, it looks like all you need is a new door.