[mettinoktay]

Yet another problematic quad is mine. Here are the problems:

• One moment it flies well; I change the battery and voila: it goes crazy with little throttle inputs.
• Sometimes the quad "pleases" to fly well (after many trials to get it stable) but right after I crash it, it is not possible to fly. It goes crazy with little throttles again.

I know it is not a tuning problem because it flies very stable with its current tuning. There must be another problem here. Gyro initialization could be the problem but 'zero gyros while arming' is unchecked and I have armed the quad at level surfaces at all times. Right after I crash and quad goes unstable, I can get the stability back by disconnecting and reconnecting the battery right where the quad stands. All I have to do is to do it until stability is back and this is the awkward point. I would appreciate any suggestion. Thanks in advance.

[f5soh]

'zero gyros while arming' is unchecked

If you want to avoid issues with Gyro init you should keep this option enabled.
This mean the quad is perfectly still while arming.

[TheOtherCliff]

Little crashes sometimes bend or chip the props.  Bad props make vibration.  Bad vibration can make it go crazy.

In addition to props being balanced, they must "track" properly.  Look at the right edge of the prop disk while you slowly spin the prop by hand.  First you see one blade then the other.  If one is higher than the other, that must be corrected.  A cresent of index card between prop and hub can help this.  It helps to look from the side, through the center of the quad at one prop hub in front and one prop hub in back to give a reference for the prop disk of the spinning motor in the middle.