Long time lurker around here, but found all my answers in your informative posts. Well, util recently that is.
We have a strange problem with one of our multis, an X8 with Pixhawk running 3.2.
When originally built, we did not have the GPS yet, so we flew it without, in stabilize/althold only. Everything went fine.
When the GPS units arrived, (NEO M8N) we went ahead and mount it, done the usual settings/mag calibration.
To our surprise, a few minutes into the flight, after switched to althold, the copter just flips into the ground. This is not good. Looking at the logs, we can clearly see the mag2 values went nuts.
Thinking there might be something wrong with the new mag and to eliminate this question, we went ahead and changed it to the second GPS unit and redone all the calibration. The first flight went fine, so we thought that was the root of the problem, but what do you know, on the second flight, the same flip happened.
I am attaching both logs, maybe someone could figure this out.