Basically it only detects when the joysticks are moving to the left or down in a straight direction. Other directions aren't detected. So if I rotate the whole joystick, it thinks I only moved to the left and down.
I already tried the controller on a PC and it works correctly. I also tried disabling calibrations in Koopair but no luck.
Also, when I go to the "edit controller mapping" section, if I try to edit any button, it instantly assigns that button with random movements from the joysticks, like in this reddit post: https://www.reddit.com/r/WiiUHacks/comments/1fif744/when_i_map_a_single_button_on_bloopair_this/
The controller it's an Ipega 9021, it's the upgraded version.
Also thanks to the developer for this app/plugin <3