Hi i just want to tell you some observation that i made to my spark wich i have from August and until now i have 34 hours flight time and 300++ kilimeters distance.

1.It is nearly imposible to make a real good imu calibration.Compass cali can be done easily.I try many times to make imu cali due to gyro yelow condtion but after cali the drone was not in better condituon so i reset to factory defaults.
2.The internal fan makes noise when the drone moves fast.I dont think that will last more than 1000000 km....
3. The motors sound is diferent than first power up. (not hard land crash or anyting else)
4.Auto exposure in camera sucks bad
5.The wifi pass sticker inside spark has completely erased..
6.I noticed minor wear in the batterys stop in spark body

I have nothing to say about batterys controller and other accesories

Never crashed droped flyaway hard land etc..

Please provide the following information:
1.Can you provide a video about the sound of the motors?
2.What is the model of your device?
3. What is the error message when you failed to calibrate your IMU?
Please try to open airplane mode and see if the wifi connection gets better.