Oven keeps flipping the circuit breaker
New GE Monogram ZET1 wall oven installed in March 08. Everything works fine, even did a clean cycle on it. About a month ago, it started flipping the circuit breaker, usually during preheat but sometimes during cooking too. It's done it on oven setting and also on broil setting. It seems to be happening more often now, to the point where it's frustrating. It's on a dedicated 40A circuit, which is enough per the specs. Whom do I call first: the GC whose electrician installed it or GE? Thanks.