Hi @Utsav_Dabhi 
You have registered your servlet with path: /bin/custom/saveFormData but you have retrurned the form action as request.getResource().getPath() + "/submitForm", which is why the correct servlet is not getting called.
Update the getAction method RegistrationModel class:
public String getAction() {
        return "/bin/custom/saveFormData";
    } 
Ensure that your servlet is registered correctly and available in OSGi. 
 
-Vikas Chaudhary