I am sure it is something simple I am somehow overlooking.
Vehicle has previously operated fine, with many launches in alt hold, and loiter mode.
Now, any launch in either mode causes an instant ground loop (pitch direction, Nose up and rolling backwards every time).
Vehicle launches fine in stabilize, and doesn’t shift position at all when converting the airborne vehicle from stabilize to alt hold or loiter.
Somehow I am sure this is an operator induced problem, just can’t resist frolicking about in the full parameter list. Any hints of where to begin unraveling problem would be greatly appreciated.