We have a script that does a HTTP callout to create a PDF, the callback saves this PDF in Salesforce as a document.

We have this working for multiple objects and this works fine. But for one type, one user, has an error that we can't seem to resolve.

The user is a System admin, other system admins can run it without issues, even profiles with less rights (sales user) can run it without issue.

But whenever this user runs it, he gets this error that we don't understand:
 

System.DmlException: Insert failed. First exception on row 0; first error: UNKNOWN_EXCEPTION, common.exception.SqlNoDataFoundException: ERROR: query returned no rows
Where: PL/sdb function doc.contentfolders.get_root_fdr_details(character varying) line 16 (SFSQL 286) at SQL statement
SQLException while executing plsql statement: {?=call ContentFolders.get_root_fdr_details(?)}(07H09000000D1Dj)
SQLState: P0002
Where: PL/sdb function doc.contentfolders.get_root_fdr_details(character varying) line 16 (SFSQL 286) at SQL statement
File: plsdb_exec.c, Routine: exec_stmt_execsql_body, Line: 3307
[conn=STANDARD:1:1:108918:1]: []
Class.HttpCallout.processContract: line 77, column 1

Callout calloutObj = (Callout)JSON.deserialize(calloutString, Callout.class);

HttpRequest req = setupHttpRequest(calloutObj);
HttpResponse res = makeRequest(req);

Quote q = [SELECT Name FROM Quote WHERE Id= :recordId LIMIT 1];
ContentVersion conver = new ContentVersion();
conver.ContentLocation = 'S';
conver.PathOnClient = 'Contract.pdf';
conver.Title = 'Contract_' + q.Name;
conver.VersionData = res.getBodyAsBlob();
conver.Type__c = 'Contract';
insert conver;  <=== Line 77