Data corruption when printing or exporting a report from SSRS to Excel or PDF [on hold]

When the users are exporting one of the reports to Excel, the following occurs: a row is being taken from one of the groups in the middle of report and it replaces the first detail row of the first group like this:

In preview:

Business Unit 1
    Plant 11 <-----
    Plant 12      |
                  |
Business Unit 2   |
    Plant 21      |
    Plant 22      |
                  |
Business Unit 3   |
    Plant 31 >>----
    Plant 32

So Plant 31 under BU 3 replaces Plant 11 under BU 1 (the entire row with all data, not just plant name field), and also remains under BU 3 as it should.

As long as the report is viewed in SSRS preview window, the rows are where they belong, but as soon as report is exported into any physical file, the first row is replaced with Plant 31. The same probelm occurs when the report is printed.

When report is viewed in Visual Studio and exported into Excel or PDF from there, the row overwriting does not occur. This is why I am left wondering if it is this old server which does not have any updates since SP2 is the culprit.

Question: Is that sort of corruption addressed in any of the Cumulative update packs issued after SP2 which we are running (10.50.4000)?