Jaggery WSO2 validation issue

While trying to register an API in wso2 application(written in jaggery), I am having a validation issue in the form i.e. I want a checkbox default checked and should validate when submit the form. I used 'checked' or 'checked=checked' it made the checkbox default checked but on submitting it's throwing an error that option/tier not selected. After that, when I uncheck and check the checkbox again it's submitting the form successfully. Can anyone please suggest what's the problem? Really appreciate your help and thank you in advance.