If you are running a mode that uses the baro (like Altitude Vario), but your baro is feeling the prop blast, that can happen. Prop blast makes higher pressure which is assumed to be "altitude too low" and it shoots up hard, prop blast is worse, shoots harder and higher, runway feedback loop that basically produces full throttle till you stop the motors.
If your PIDs are too high you can get invisible oscillations which forces the motors to act like they have half power even when it is set to 10%.
Bad vibrations can cause these oscillations in some circumstances too.