With it sitting for 40 minutes or more, you might be overheating IMU, causing issues with calibration.
Let it cool down, and try flying , as soon as you have home lock, a few minutes after startup!
So turn on, wait for home lock, fly. See if Any issues? If not, then possibly a heat issue, as with any
CPU, they run really hot anyhow!
I agree above,
Do a fresh IMU ( advanced calibration ) keep level and stable while performing cal.
Then Tx calibration
Then before first flight, fresh compass calibration
( NOTE: when doing compass cal, SLOW, STEADY, LEVEL ROTATIONS IS BEST
No need to race through it, you have plenty of time
Turn everything on ( controller, extender, phantom, iPhone )
Connect to wifi
Enter calibration mode
Pick phantom up off the ground about 1 foot up keeping it level ( spin 360 degrees around )
Yellow lights turn green
Flip phantom so front ( camea ) is facing ground ( 360 spin again )
Now light will go to
Blinking yellow ( less than 6 satellites )
Blinking green ( more than 6 satellites ) and home lock
Fly! ( I know you probably already know this, but just in case ) some people rush through
Calibration, not getting accurate reading!
I'd try that first, if still an issue, open it up, and inspect EVERYTHING, pinched wires, loose connections, ect!
Then ( if all else fails ) return, or send in for repair ( could be faulty circuit, or bad solder joint
Somewhere? ) I'm no tech, let our friends at DJI deal with the issue, as they are experts, and have the necessary
Equipment, to diagnose electronic circuits!
Jerry D
USA
( J Dot )