Ok...I'll probably get flamed for this.  

I took both out for a flight today - same winds, same location.

I can't help but notice that the Phantom was more "obedient" - it doesn't YAW and move by itself so much.  As for the INSPIRE - I noticed there will be times the camera, and/or the craft would YAW by itself.

I use "Follow Mode" for the gimbal... I do compass calibration....

Is there something I'm doing wrong?  

Mine yaws by itself as well.  Pain in the ass, eh?

Did you do a IMU calibration yet ? if not do so. My inspire is rock solid way more so then any phantom i have as well

This is not normal behavior,  have you contacted support?

Ok my bad... I haven't done an IMU calibration.

The function is hidden in ADVANCED SETTINGS, with the warning "Only Advanced users should modify these settings. Make changes with EXTREME CAUTION."   I don't consider myself an advanced user, and none of the manuals mentioned anything about IMU.  

I hope this solves the problem.  Strange thing is after calibration... after a while I check again it says I need to calibrate again - all these while with my craft lying still on my bedroom floor......

Looks like I'm not the only one with the problem:

Hmmm... is there anyway to do an advance calibration in South East Asia?  Our weather temperatures are consistently 30 degrees celsius, and every time I want to do an advance calibration the APP reports over heating?

darickyeo@gmail Posted at 2015-1-14 09:22
Hmmm... is there anyway to do an advance calibration in South East Asia?  Our weather temperatures a ...

DJI stated today that there is a known IMU bug causing crashes on auto takeoff. Apparently it causes the yaw issue too that I have seen myself. A firmware is coming to fix. In the meantime, they say to perform an advanced IMU calibration to be safe. (Their post is on rcgroups if you want to see it. )

AnticipateMedia Posted at 2015-1-14 09:30
DJI stated today that there is a known IMU bug causing crashes on auto takeoff. Apparently it caus ...

Yes I know about the upcoming firmware, I know about advance calibration - it is just so hard to do an advance calibration in a hot climate I live in.  

Every time halfway through the calibration it will say overheat....

use a walk in fridge