RDLC list report lines appear twice

Kowa

We have created a simple report to show customer ledger entries using the layout suggestion.
For some reason, all ledger entries appear twice when run under the RTC. In the CC it works.

Similar problem as in this thread.

Kowa

We added code like this in the VB Sections

=IIF((Previous(Fields!Gen__Journal_Line_Line_No_.Value)
=Fields!Gen__Journal_Line_Line_No_.Value)and
(previous(Fields!Gen__Journal_Line_Journal_Batch_Name.Value)
=Fields!Gen__Journal_Line_Journal_Batch_Name.Value)
and(previous(Fields!Gen__Journal_Line_Journal_Template_Name.Value)
=Fields!Gen__Journal_Line_Journal_Template_Name.Value),TRUE,FALSE)

to avoid these double lines, but it is strange why this is necessary.