Export/Print custom headers

Hello,

i got a problem which looks like a DayPilot Bug. We should have the newest version (v.7.4.2923.0)
As soon i want to use custom headers, the headers in the exported .png look bad. Thats how i do the custom header
....
dpsProjekteExport.TimeHeaders.Clear();
dpsProjekteExport.TimeHeaders.Add(new TimeHeader(GroupByEnum.Year));
dpsProjekteExport.TimeHeaders.Add(new TimeHeader(GroupByEnum.Month));
dpsProjekteExport.TimeHeaders.Add(new TimeHeader(GroupByEnum.Week));
....

Is this ta knowed problem?