InvalidPasswordException with 123456=abcABC

Hi AWS team,

our user pool is configured like this:
Email address or phone number - Users can use an email address or phone number as their "username" to sign up and sign in.
=> Allow both email addresses and phone numbers (users can choose one)

Our password policy is:
Minimum length: 8
=> checked - Require numbers
=> checked - Require special character
=> checked - Require uppercase letters
=> checked - Require lowercase letters

We use Amplify to sign up users with email and password like this:
signUp({
email: mail,
password: password,
username: mail
})

Regarding your documentation from here
https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-settings-policies.html
the "+" and "=" are in the list of special characters.
So it should be possible to sign up users with the password
123456=abcABC or 123456+abcABC

BUT we get "InvalidPasswordException - Password did not conform with policy: Password must have symbol characters".

It works when I replace the = with !

Any information why this happens with the characters "=" and "+"?
Do we need to change our configuration?

If you need more information, just ask. =)

Best regards,
devBaum