2-up COULD cause an issue, but my pillion never leans on it. What I think happens is the base flexes while flopping around on the mount, especially if you overload it or, like me, put a cargo net to carry stuff up inside the lid (higher center of gravity). The material is rather thin, and there are natural stress points at the lower front, either side of the "tongue" that goes into the mount. A few have failed, and the aluminum plate was necessary for a reason. My advice, don't overload it.
I am getting a replacement for cheap, however if it fails, I'll go Givi or something like that. They aren't as tall, but wider and you can keep your stuff in the lower half.