Embedding existing tablix with several group levels into a main tablix

In a new ssrs 2008 report, I am embedding 18 tablixes into 1 main tablix This is due to all the data will be related to a particular student. Each of the 18 tablixes will be a unique report where the user utilizes a report parameter to determine what report(s) they want to have executed. This process has 1 dataset that is being used. The rows that are selected for each report is based upon the column called report_number. Each tablix (report) has a filter parameter that is used to determine what rows from the dataset apply to the particular report. The columns in the dataset that are not being used for a particular report have a value of spaces or zeroes in those columns.

This process has worked fine until an existing report has embedded in the main tablix. This executing report has 4 levels of groupings were summarization counts are made at different levels. The error message that is displayed is,

'The tablix 'Tablix1' has a detail member with inner members. Detail members can only contain static inner members'.

To solve the problem so far, I have used the following links:

  1. http://blogs.lessthandot.com/index.php/datamgmt/dbprogramming/reporting-services-error-the-tablix/ ,

  2. http://forum.mibuso.com/discussion/65638/the-tablix-has-a-detail-member-with-inner-members-detail-members-can-only-contain-static-members , and

  3. https://social.msdn.microsoft.com/Forums/sqlserver/en-US/2df504fe-1e24-4513-947a-a8fd399979d4/adding-table-to-a-list?forum=sqlreportingservices .

These examples work fine for 1 level of a report. However this report has 4 levels of groupings. One of the comments in the first link said to 'delete group only' would solve the issue. However this does not work in my case since the report group has already been deleted.

Would you tell me what I could do to solve the issue?