It Won't Arm
The arming-disable flags are the answer — how to read them, and what each common one means.
Video Static & Noise
When the noise appears tells you what it is — throttle-synced, distance-based, or ever-present each have different causes.
Motor Problems
Twitching, not spinning, running hot, desyncing — four motor symptoms, four trees, props off for all of them.
Flips on Takeoff & Drifting
The instant-flip trio (motor order, direction, props), and which kinds of drift are bugs versus physics.