Hi, this and the related issue (Gramps Web export issue [XML - can only concatenate str (not "NoneType") to str] & [GEDCOM - HandleError()]) looks like you have a corrupted object which has “None” as handle somewhere. Can you please open the browser dev tools (F12), look at the response of the respective API call (/api/person/somehandle/...) and post the JSON here (after redacting sensitive data, if any)?