The armed idle speed is above the in-flight minimum

What ArduPilot says:

• …SPIN_ARM > …SPIN_MIN

MOT_SPIN_ARM is how fast the motors turn when armed and waiting on the ground; MOT_SPIN_MIN is the lowest output used in flight. Both are fractions of the output range, 0.10 and 0.15 by default. ArduPilot requires the idle to be no higher than the in-flight minimum, and here it is higher.

What to do, most likely first

1. MOT_SPIN_ARM was raised so the motors start reliably, and MOT_SPIN_MIN was left where it was.

   FixRaise MOT_SPIN_MIN as well: at least 0.03 above MOT_SPIN_ARM, as the Setup & Tuning Guide's idle step describes.

2. One of the two was typed as a percentage (10) instead of a fraction (0.10).

   FixEnter both as fractions of 1.

Parameters to look at

Where to do it:Setup & Tuning Guide