This something I'm happily doing away with in my Open Solo modifications. As designed, the Solo uses a smart shot called Return Home or Rewind for failsafes and for when you push the home button. When in these "smart shots", the A & B buttons are disabled and the so are sticks. The only thing you are allowed to do is push FLY or Pause. And I think you can use the left stick for camera pointing. You can't change modes or do anything else. This is like 4 different layers of unnecessary complication and unnecessary points of failure for something that is supposed to be a failsafe. If anything goes wrong in any of that complication, you're screwed. On numerous occasions I've had the solo get basically stuck in the air because damn sticks and buttons were disabled. I had to watch it just sit there hovering until the battery died and it crashed. And I'm not the only one. Oh, and there is also a line of code in there that locks out the buttons when the EKF goes bad, which is likely what happened to the OP. This is also stupid. Locking the operator out of controlling the copter in an emergency is insane. Normal controls do not get restored until it is in the final landing phase.
In my revision of Open Solo, I have dispensed with all of that crap. The failsafes use ArduCopter RTL mode, plain and simple. None of this smart shot complication. The buttons remain unlocked. The sticks remain unlocked. You can push any button you want and take control in any way you want. And in the mode change callbacks, I modified it to cope with botched smart shot exits, which is what causes a lot of the grief. Any mode changes also fires off code that ensures buttons and sticks are in normal modes, not remapped or locked out. Open Solo will also be safer solo. Making solo safe again.
