Unstable altitude

Hi, boys :slight_smile:
We are making our own multicopter and we got the problem. After turning on the vehicle (not flying, it remains on the ground) the altitude from GPS is starting to rise, then it goes down for about ±20 meters. Barometer works fine, it shows the altitude rather accurately. But in hold-altitude mode our copter is using the GPS altitude and vehicle goes to flying up and down for these ± 20 m.
So are any solutions to to keep permanenst GPS altitude? Or how to use Baro-altitude in hold-alt mode?
Thx :slight_smile:

P.S. or is it the baro-altitude unstable?

Was this outside with a good GPS fix? Sharing a log can be helpful for finding the problem. http://logs.px4.io/