Strange altitude behavior almost lead to crash - help needed

I have been trying to deal with a problem that has to do with altitude hold. I see it in both loiter and althold modes. Basically the quad is holding altitude fine for most of the time, there are certain conditions which I have not yet determined that cause very large changes in altitude. Sometimes it happens when yaw is changed others it comes out of nowhere.

In the attached log the flight started fine but several seconds into the flight and in loiter mode the altitude became extremely noisy. This led to very large changes in throttle (from 100% to almost 0%) causing a free fall followed by a recovery. It did not crash but it was a close call. I know my vibration is high, can some of the experts confirm this is the problem?

I find it strange that the altitude noise is intermittent, as you can see several seconds after takeoff it was fine and got noisy all of the sudden. The vibration actually drops when the altitude becomes noisy, this is likely because of the motors shutting down temporarily.


Those vibrations are a huge problem. You also seem to have barometer spikes… is your barometer covered?

No reply here. This problem is similar to my unsolved question. Did you solved the problem? Is it ok The semi opaque case supplied with the board? I opened it on one side… Could this be the problem?