[suicideneil]

Sounds like maybe a broken solder joint inside the esc perhaps on one of the motor leads, or one of the phases has died- any smell of burnt or hot electric when it's powered on?

I would just contact traxxas customer support, tell them it died after 2 runs, you've tried a different motor & it needs to be sent in for repair or replacement- should be free if it's less than 12 months old.