Any body notice that the second IMU takes a lot longer to warm up than the first IMU? If you turn everything on and once you get the ready to fly come up in the top left of the GO4 App go to the sensors page in settings and check the state of the IMU, mine shows the first one all green and good to go but the second one is still warming up and it takes quite some time before it does come online, it doesn't stop you flying tho and I haven't noticed it before the firmware upgrade and the latest Android v4.1.4 App           

Just out of curiosity I went to see!
And In my case both IMU warm up  at the same time !!

The readings in the sensors will vary between IMU1 & 2. The left side of the scale represents no bias or adjustment needed (which is good), so anything in the first third of the scale is seen as excellent represented by green, the next third of the scale is good represented by yellow, and then poor (red).
So in an ideal world small green bars would be the better option.

My IMUs warm up in a short period of time, as far as I'm aware the bias scale does not relate to warm up time.

I've just downgraded firmware to v01.02.602 and now both IMU's warm up at the same time.

M109 Posted at 2017-8-2 15:50
I've just downgraded firmware to v01.02.602 and now both IMU's warm up at the same time.

I got the strange double startup sound with the current firmware which I associate with each IMU waking up. The downgrade fixed it.