Page break not working when exported to pdf

SSAS and SSRS
1

I have created a report with 3 grouping levels like Category,Proposal Header and Proposal Details.
The report page orientation is landscape(w=14in, h=11in).
As per the data, Proposal Header row is always a single row and always exist.
Proposals Details may or may not exists and if they exist they always have 4 row details.

A page can usually fit two sets of Proposal header and details section due to page header section.

I need a page break only if the Proposal Header changes. In other words, Proposal header and details
should be on same page.
On the proposalHeader group properties, I set the page breaks option to
"between each instance of a group".

The report displays as expected when you preview it, but when you export the report to PDF, it doesn’t display correctly.
The records that are part of Header and detail group are breaking mid-way when the page gets full and those records are moved to next page.

Am i missing any property setting.

2

I may be off here because I'm still fairly new to SSRS but have you tried putting the page break on the Tablix instead of the group? My thought process is that having it on the group renders fine in SSRS but since the PDF is more of the graphical output, it may need to be on the actual tablix control so that the PDF export actually works. But, as I said, I could be way off and I don't have any way to test it at the moment.