Here in AZ where summertime air conditioning loads can become continuous loads we do see breaker meltdowns. However, the bus always gets damaged and it will spell death for any subsequent breaker installed on the same stabs. Even cleaning/sanding them is no help for very long. Some of the buses are plated, and the plating burns thru. Many times the whole panel will melt down. Interesting note though, every panel I have ever seen that melted down was a Siemens. Never seen any other brand melt down. Not trying to badmouth Siemens, just an observation.
