Field paths within hooks are not correct. For example, an unnamed tab containing a group field and nested text field should have the path myGroupField.myTextField. This is how it is currently formatted within form state, which is correct. However, within hooks that path is formatted as _index-1.myGroupField.myTextField. The leading index should not exist, as this field is considered top-level since it is located within an unnamed tab. This is evident when creating an API request with invalid data and reading the validation errors in the response. The form in the admin panel, for example, returns this response with incorrect paths. The only reason this was never caught within the admin panel is because we merge those errors with the ones we've saved to form state.