This is a load bearing part, not simply a guide, so bonding or riveting are not viable options.
I suspect that the original was welded, and a careful look for the remnants of a bead, or at it's mate can confirm.
In any case, there's no easy fix, so either a clamp on stop, or full housing with clips are the options, though IMO, this should qualify as a defect under the warranty policy. Visit the dealer or email the maker (or both) and see what they say. If they won't make good with at least a substantial credit towards a replacement (based on how long you've owned it s. projected life), you might consider small claims court.
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