Strange elevator response to stick in FBWA and Manual mode

When I give full UP elevator by pulling the elevator stick all the way down and HOLD it, the elevator first deflects fully, but followed shortly (about 1 second) by returning to neutral position. This happens in FBWA and Manual mode in Arduplane V3.9.6

But when I give full DOWN elevator by pushing the elevator stick all the way up and HOLD it, the elevator deflects fully and stay there, NOT returning to neutral position in both the above 2 modes.

Is this normal ? If yes, what is the logic behind ?

If my plane is powerful enough, and I need full UP elevator during takeoff (say to clear some obstacle), this returning to neutral of the elevator is undesirable.

Volantex Ranger EX 757-3, Pixhack 2.8.4., Arduplane V3.9.6

Can anyone shed some light on this issue. Thank you.