Dexter Door sent me a replacement door bottom, which they call a Strut Surround Sill, and a foam gasket tape for same. They also sent a new strut. I have to send back the old parts.
From me, they needed a picture of, or the numbers on, the build sticker on the inside of the door jamb area. And the VIN and purchase date.
The new part is the same as the old except when they squeezed the ball stem onto the backer plate, they did it in a way that did not curve the backer plate upward. It still doesn't look super strong, but they think it is strong enough, so I will find out.
The new strut is quite a bit slower acting, at least when new. I had already bought a 10 pound strut on my own. I tried it, and to me it behaves about the same as the stock 20 one did. Meaning the door flies quickly to the end of the travel and then flexes back and forth. With the new one that Dexter sent, the door moves out more slowly. So I am using it.
If you want to call them, the number is 574-848-4491. Warranty dept is x263. Mine was a bit out of warranty but they honored it. Assuming the price was reasonable, I would have paid if I had to. I tried to fix my old one, but there is so little clearance for the stud, and strut end, on both top and bottom that I could not get a satisfactory setup. If I could have found a really short ball with a threaded mount stud, I could have done it. But I couldn't find one shorter than the one I bought, which simply was too tall once the strut was attached to it.
Here is a photo of the stud mounting on the new part.