Until today my APM2 has performed very good, but now it has changed it mind regarding booting with power from the output rail. And yes I have the JP1 connected, and tried to hardwire it just to be certain.
And it is not a brown-out, as I have also tried to power it from an external powersupply.
Now it will only boot up from either input rail or USB power.
Does anybody have any suggestions regarding this matter?