A defective chain may break once, but the odds of a defective chain causing multiple breaks are extremely low.
need to know more.
Is it a Sram or other brand chain?
Is it breaking at the same or different places?
Are you closing it with a new connector link, or the same one, or simply using a chain tool?
Are plates cracking, twisting, or falling off the end of the pin on one side, then bending open under load?
Did you correctly measure the chain so it clears the large/large combination plus at least one inch?
Even without seeing your answers, I suspect your problem is related to how you're closing the chain, and that shifting is forcing the plates over the ends of the pin.
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Chain-L site
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