Guys hello!

On my TRex 500 DFC the pitch works slowly. In the range of about zero (hovering) the pitch is very unresponsive, inaccurate. The helicopter falls down. When the pitch becomes larger the response is absolutely normal. What parameter is responsible for this?

I tried to calibrate the ESC, different governor modes, but nothing changes. It is difficult to hover the helicopter at a small pitch.

Spirit GT
HW 80A V4
about 2500 rpm