My report consists of a Report Header and a Detail section. Their design-time height is totally less than 20mm. There are no PageBreaks or GroupPageBreaks and all KeepTogether properties are False. In Print Preview, the Detail section starts from the second page when the PaperSize Height is 88mm or less. This is not expected as there is sufficient space left after the Report Header. The Detail section starts rendering from the first page only when the paper height is more than 88mm, which is the expected behavior.
See the forum post Report Header and Detail Section does not print together for the report definition that allows reproducing the issue.