Can someone help me on this Error : KoBoCAT error 400

[Dr Tanupriya]

Unexpected KoBoCAT error 400: {"detail":"ODK Validate Errors:\norg.javarosa.core.log.WrappedException: Error evaluating field 'group_cw7rd12': The problem was located in Relevant expression for ${group_cw7rd12}\nXPath evaluation: type mismatch \nconverting to date => org.javarosa.xpath.XPathTypeMismatchException[The problem was located in Relevant expression for ${group_cw7rd12}\nXPath evaluation: type mismatch \nconverting to date]\norg.javarosa.core.log.WrappedException: Error evaluating field 'group_cw7rd12': The problem was located in Relevant expression for ${group_cw7rd12}\nXPath evaluation: type mismatch \nconverting to date => org.javarosa.xpath.XPathTypeMismatchException[The problem was located in Relevant expression for ${group_cw7rd12}\nXPath evaluation: type mismatch \nconverting to date]\n\n>> Something broke the parser. See above for a hint.\n\nResult: Invalid"}