Couple of questions, are you interactively entering data or are you merging data?
What is the xfa template version or what do you have chosen as the Target version?
If you click on the cell in Designer and go to the Layout tab, under Height is the "expand to fit" checked?
if you has another cell which is not allow page breaks(for example：text cell) in the same row, That will lead to the problem。
in that case， you can use a subForm wrap the "text cell"， that's all。