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Hi, I'm Mike G and I'll be assisting you. I would first suggest swapping the circuit to another breaker on the same phase to see if it still trips in its new position. This will show if the breaker or the circuit is the cause.
You need to verify as directed. If they are split twins, ones that can be sepersted from each other, they have poor attachments to the buss and often open up allowing for arcing and heat which trips the breaker. If split twins replace both with a single twin breaker. They don't have that problem.
You need to test as suggested before buying a replacement. Verification is required.