Nested sub-reports work in studio preview and web-ui but not on export

Question

I have created a report with two level of nesting for sub-reports. While I preview in studio, or run in the jasper web console the report works but when trying to export as an XLSX, the inner nested reports gets excluded from the excel file. Can someone please shed some light on the reason for such behavior? The nested sub-report element which is excluded while exporting is in the title section of its immediate parent.

The reason for nesting is to have a master report with multiple groups. Each group is having a sub-report to be rendered in each individual excel sheet, with a break element in between them. The sub-report again has two sections one table and another graph. While the table is embedded in the sub-report, the graph is created as a separate report and is embedded again as a sub-report within the first sub-report. Following structure explained -

Master Report-

                (1st child Sub-report) )Report Sheet 1

                                                      (2nd child Sub-report) Graphs

                                                      Table

               (1st child Sub-report) )Report Sheet 2

                                                     (2nd child Sub-report) Graphs

                                                     Table

Each report and sub-reports have the following parameters set -