Honda GX670 trips breaker, won't immediately restart

I have a Honda GX670 repowering an old bobcat skid steer. Recently the engine started tripping the 3amp circuit breaker in the key start module after running for 20-30 minutes. Upon resetting the breaker, the engine won't restart until after 15-20 minutes. The cycle repeats.

I tested the regulator-rectifier at room temperature and it tested okay. I suspected it was going wonky after getting up to temperature, so I replaced it. Replacing the regulator-rectifier did not solve the issue. Any ideas?