Bug in Paginated Reports

I've built a paginated report with merged column headers, one of which contains vertical text.

It works fine when I preview it in Report Builder in both normal and print layout.

When I open it in the Power BI service, the vertical text is cramped into the top row of the header cells.
Report builder view:

Power BI service view:

Is there a way to overcome this please?

The Cognosaur.