Unfortunately the answer is - send the unit in for service.  The ESC, or Electronic Speed Control, translates the microprocessor's instructions into motor speed.  If the ESC were to fail in-flight, the motor for that prop could stop running altogether or run at an uncontrolled speed.  Either one could result in a crash (a quadcopter can NOT stay airborne or maintain control with a motor out).  If you crash your aircraft, DJI will want the flight data from the internal storage on the unit, which will reveal the repeated indications of an ESC error and the fact that the bird was repeatedly flown anyway, and that in turn may affect your ability to recover anything under warranty.

I think you made the right choice.  Having a motor stop in flight would not be a good thing.  They can also check as to why you are getting the gimbal calibration error.

I was on my third flight outdoors on my brand new DJI Inspire 1 that I waited two months for.  I then took my I1 inside to test the indoor flight capabilities only to receive the 'ESC' error code.  After reading this very forum I sent mine in as well.  5 weeks later it was returned from DJI stating there was nothing wrong with my aircraft.  I just unboxed it went through compass cal., firmware upgrades (RC, 5 batteries, aircraft)  I then fired it up and went to simulator mode to test my new stick settings and bam, ESC error code again.  I then took the aircraft outside of which it fired up without issue.  I am curious if the ESC error code has to do with being inside and no GPS signals?