check 0:11 in this video,
https://youtu.be/NSpmnMA7Gtoif you did not touch the flight stick then,
it shows that your flight stick has not been properly recognized by ReaSnow S1,
that axis shall be 0 when they are untouched.
are you using Saitek X52 or Saitek X52 Pro?
btw, no need to change the deadzone,
this issue is not caused by that.