I think you're talking about the plastic/chrome gutter cover that's falling off, not the actual gutter. The gutter afaik is formed where the top is welded to the sides and is integral to the body. In other words, it can't come off unless the whole body is falling apart.

Because of that, I think your gutter-mount Yakimas are the strongest you can buy. The other styles mount on the roof racks, or rest on the roof, and that's not as strong as the gutter.

Take a look... does that sound like what's happening?