Lack of centering elevator.
Video was taken with +-100 range. I have checked also with +-80 range (Walkera Spektrum range). There is no difference.
Summarizing after detailed check.
When SAFE is not active, everything is OK for all steering surfaces.
When SAFE is active elevator movement UP gives effect at once.
Elevator movement DOWN gives 80% of throw at once, the remaining 20% is done during approx. 2 seconds. For Beginner, Intermediate and Expert. Seems for me this is the gap of "0" position. For Beginners mode throws are limited, so this harder see, but exists.
For ruder and ailerons everything is OK.
I checked it with 3 servos and 2 Rx.
PANIC mode allows only to move up elevator.
vimeo.com/155432226