OBIEE 12c: Parallel Download of Export To Excel By Same User Using Two Tabs On Multiple Reports Hangs:
When one users tries to export more than one dashboard/report to excel at the same time, the first export completes successfully where as the second export hangs showing “Processing Export To EXCEL 2007”.
The hang occurs even when the same user tries to export different dashboards at the same time using different browser tabs.
However, the download is successful when user tries to export the dashboards/reports one at a time.
Below message is noted in Oracle BI Presentation Services log(Sawlog):
[2020-08-04T09:02:58-04:00] [OBIPS] [ERROR:16] 
saw.threadpool.downloadpool] [ecid: ]
[tid:] [SI-Name: ]
ThreadPool<DownloadPool:1>: Worker thread job errored out. The dashboard is being exported by this user
This product feature is working as designed. OBIEE UI restricts multiple simultaneous downloads at the same time to prevent overloading the system with large download requests.
Once the first export completes, second export can be initiated. With multiple downloads, multiple threads are spawned causing severe performance issues with large reports and hence its being restricted.
This is resolved in 18.104.22.168.200714 and later.