Its an old multicopter and everything is old on it, but it flew perfectly on a quad and the stubbern half of me wants to find the problem with this setup. 
I took it apart and resolder and moved around the PM, Telemetry, LEDs, UBEC, retractable legs-driver, cables, … to get less interference with the APM.
I have also made the APM more encapsulated in foam. Also changed the foam inside the APM for the barometer.
I have also used alu-tape on the bottom plate (PDB for to get rid of more interferences.
But the biggest problem is that the firmware dont work…
Using 3.1.5 was something to do regarding to many having issues with the barometer using 3.2.1 which seems much more sensitive and I tried that too, but with problems. Cant compass calibrate (My try to find a solution here on the forum: Gets binding error calibrating Compass ).
Yep…