Kibana meet this error

kibana version: 6.4

error: {"error":{"root_cause":[{"type":"parsing_exception","reason":"Expected [VALUE_STRING] in [docvalue_fields] but found [START_OBJECT]","line":1,"col":107}],"type":"parsing_exception","reason":"Expected [VALUE_STRING] in [docvalue_fields] but found [START_OBJECT]","line":1,"col":107},"status":400}

Did you make a script field ?

what version of Kibana are you on? what happens when you remove the offending visualization?
with regards