Like any other multirotor controller, Autoquad does not like vibrations. The filters are able to handle some noise, but if it gets over a certain level it will have a negative impact on stabilty and can in extreme cases lead to runaway state in PH/DVH and Mission modes.
Example of bad vibrations on a Y6 at hover throttle (this is a quick restrained ground test). In flight, the AQ would oscillate up/down quickly and randomly, and also felt very “twitchy” when trying to control it.
Here is the same Y6 with a lot of the vibrations tamed by careful propeller selection and balancing, but still showing vibration problems. The bigger spikes are vibrations which set in intermittently.
Compare the above to these graphs taken from an actual flight test where the Y6 was not suffering from (severe) vibration problems and flew normally: