Nevermind i disassembled hederos mig and i learned how to fix it @Jorgebr

another option is to place a wing structure hidden inside the rudder
because the sp doesn’t count the fuselage as a wing or anything that generates stability or support, so it’s like there’s no rudder there, you’ll probably also have to put a wing hidden on the control surface

Try to put more weight on all the pieces without unbalancing the center of gravity, if it works you decrease the weight little by little until it gets better. If it does not advance. You can appeal to a gyroscope.