TextFormField shrinks on error validating FLUTTER

I am learning Dart/Flutter, and I got a error that I just can't figure it out.

no problem with this textfield:

TextFormField(
                keyboardType: TextInputType.emailAddress,
                controller: emailController,
                obscureText: false,
                focusNode: emailFocusNode,
                textInputAction: TextInputAction.next,
                decoration: const InputDecoration(
                  border: OutlineInputBorder(),
                  labelText: "Insira o Email",
                  prefixIcon: Icon(Icons.mail),
                ),
                validator: (String? value){
                  if (value != null && value.isEmpty){
                    return "Insira o Email";
                  }
                  return null;
                },
              ),

but with this one the hight of the Textfield shrinks

AnimatedContainer(
                duration: const Duration(milliseconds: 500),
                height: registerAuthMode ? 65 : 0,
                child: AnimatedOpacity(
                  duration: const Duration(milliseconds: 500),
                  opacity: registerAuthMode ? 1 : 0,
                  child: TextFormField(
                    validator: (String? value){
                      if(registerAuthMode){
                        if(value != null && value!.isEmpty){
                          return "Insira a Senha";
                        }else{
                          if (value != passwordController.text){
                            return "As senhas não são Iguais";
                          }
                        }
                        return null;
                      }
                      return null;
                    },
                    controller: confirmPasswordController,
                    focusNode: confirmPasswordFocusNode,
                    obscureText: obscureText,
                    textInputAction: TextInputAction.done,
                    decoration: InputDecoration(
                        border: OutlineInputBorder(),
                        labelText: "Repita a  Senha",
                        prefixIcon: const Icon(Icons.password),
                        suffixIcon: IconButton(
                          onPressed: toggleObscureText, icon: obscureText
                            ? const Icon(Icons.visibility)
                            : const Icon(Icons.visibility_off),)
                    ),
                  ),
                ),
              ),

before validate after validate

the bottom for validate

 ElevatedButton(
                    onPressed: () {
                      if (_formKey.currentState!.validate()){
                      }
                    },
                    child: Text(registerAuthMode ? 'Registrar' : 'Entrar'),
                    style: ButtonStyle(
                      elevation: MaterialStateProperty.all(8.0),
                    ),
                  ),

my guess is that has some kind of problem with the widget animated container and animated opacity

again, im pretty new to this, so if I did something wrong or ask for help the wrong way sorry.

I can't figure it out. but has to do something with animates opacity and/or AnimatedCointainer

EDIT:

so I checked this : Validator error message changes TextFormField's height

and kinda worked.

I put an error style inside the decoration from the textformfield.

decoration: InputDecoration(
                  errorStyle: const TextStyle(fontSize: 0.1),

and this was the result: didnt shrink but no error msg

but now de ERROR dosent show anymore. the border turn red, but no more insert your password"or something like this.

Removing height from animated container will help.