That was also my Problem!
I had a crash today. Just recently Loiter/RTL work pretty good for me but today my quad flew away from me after switching to RTL and came down hard. Mag declination was ok at take off (checked RTL/Loiter/SimpleMode nearby). After collecting the leftovers I checked the settings again and found that the declination had changed to an absolute strange value and from east to west !
O.K I have checked the mag dec via the log file and graphed it. there are some serious spikes in it and it isn`t smooth in any area. So i selected first person kml in in the log download tab and played it back via google earth, which I assume should give you a first person view of your flight via the data collected from your flight.
Well it was like a blur off spinning horizontally and vertically, which I assume can only be put down to the onboard compass? I have my board mounted at least 3cm from any voltage wires or metal objects. And have had it placed 5cm beforehand, but because that made no difference I moved it back. Other boards like the DJI Wookong have the compass something like 15 - 20cm away from anything on its own, on my apm2.0 this is not possible as I have the daughter board with gps so I believe that option is not available to me? I will try and but some extension leads and place the whole board as far away as possible, but on my Tricopter it will be about 20cm up from the base so will look like a flying tower block, however I will try it and report back. If anyone one else has trouble with thier gps co-ordinates I would be gratefull to hear from them as mine are out by 20 miles and I have posted this problem a few times but never got an answer to help solve the problem.
i seem to have a similar issue. I crashed my craft three tims up to now (i use crash bumpers, so usually nothing gets damaged). - See here:
Do you know any resolution ?
Have you guys found a solution to this loiter problem? mine is the same, or pretty close. mine really seems to go crazy after I hit the sticks to correct it. It will fight to go in the opposite direction that I move the sticks.
If you guys figured this out please let me know
I used to have this problem and it always has been mag declination configuration. It changes values by itself. i think most of the cases it happens is when I switch batteries.
What I would suggest:
If that is better then you can try to turn them back on one at a time to see which one is the problem. If you turn COMPASS_LEARN back on and then off again you will have to repeat the Live Calibration. Or if you wrote down the old numbers you can put them back in.