I solved the problem, but want to know, what could be the reason for
it.

I have a report in ReportBuilder, where I have a subreport. The main
datapipeline is connected to the invoice table of my database. The
subreport has a datapipeline that is connected to the invoicepositions.

I use the afterscroll event to set the master detail connection.
something like that: invoicepos.parambyname ('invoicenr').asinteger :=
invoice.fieldbyname ('invoicenr').asinteger;

If there are as many positions that the invoice has 3 pages, I get a
loop when generating the report. In designmode I can use the preview
and click on page 2, page 3 and everthing is fine, but when I click
directly on page 3, after entering the preview, it loops.

I posted this to the support of Digital Metaphores, but also want to
ask here, if it could be a IBO problem.
Here is the solution that solved my problem:

The invoice position query uses joins to retrieve related data from
several tables.
When I remove the joins, it works. When I put in the joins, it loops.
So I defined a view, where the joins are in the view. So I can define
a query without joins for the datapipeline.
If I do so, everything works well.

Does anyone have an idea why joins lead to such problems?

Kind regards
Helmut