Hi friend, I had a similar issue and posted about it a few days ago (here). I was flying in Altitude mode. Right after takeoff the drone was stable, but after about a minute it started to climb, not pulsing, just slowly and continuously, until I activated the kill switch because it wasn’t responding to my descend commands on the radio. At the time, I didn’t think about switching flight modes, that might have saved my drone.
I also had high vibration levels, but like yours they were consistent during the whole flight. Besides that, I’m starting to think vibration might be aliasing the estimated velocity and making the vertical position unstable.