Fastening stud popped off without tightening nut

Stud that joins shelf to triangular bracket literally popped off as I began screwing the nut onto it. It definitely concerns me that I was going to be setting hot coffee on this shelf. How much force will it take for others to pop out? They appear to be brazed in place. There has to be a better/safer way to fasten these studs. I sent it back.

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