ReportViewer - 创建报告时奇怪的未显示异常

I'm using the WebForms version of the ReportViewer in LocalMode. In the structure I have one main report with 5 subreports. Generation of the report is really slow (1800 report pages for around 10 minutes). While debugging, when I stop and I see the executing thread, the location is most of the time in I'm using the WebForms version of the ReportVie