i calibrate imu also gravity sensor but this seems to happen again!!! i notice one think that if drone fly very low near ground about 1,5 meter seems unresponsive but in height more than 2 meters seems work ok!! this happen to you when fly in low height??
Once it happens at about 50 cm from the ground and the other time in teh garrage about 2 m high... but passing over the car... so between 2 m and 1 m.
The official app is really nice but I think it will be very interesting to have a lists of firmwares to install in the tello directly from the app. In some cases old firmwares work better that newer ones.