I have paragraphs splitting across pages, when there is room on the previous. I resolved this issue some time back, and I know it had nothing to do with orphan lines, but I've forgotten what the solution was...been a few months since using Frame 2020.
Could it be that your paragraph has the option Keep with Next Paragraph on the Pagination tab of the Paragraph Designer activated?
And the next paragraph does not fit on the first page?
No, the next paragraph will fit on the first page. However, the Keep with Next was checked. Unchecking Keep with Next resolved the problem, in this case. However, I have had this issue before and resolved it another way when the orphan lines were changed and the second paragrah on the next page would not move up, despite the fact that the previous page had room.
Maybe the second paragraph also has Keep with Next checked?
Resolved for now. Maybe so. Will look at it again, when encountered.