Is not a valid value for the type xsd:date
If you're receiving this error, it is most likely caused by an incorrectly formatted date being sent to a Salesforce date field.
1. Add a date validation in the Form Builder to the field that is throwing the error to resolve.
See our Date Validation article for more.
2. Make sure you save your form after you've made the changes.
*You may also need to remap the field if it is still causing errors.