I think your table is not formatted with table header row options, try with applying "Example" cell as table header row then it wont change anymore even though if u r applying cell styles to next rows.
That is not the problem. The problem also occurs with adjacent table-body cells.
I've found that the problem occurs due to the order the cellstyles are applied;
Normally, I will apply the styles "left-right, top to bottom".
In the above example, the style in cells with "how" and "it" overwrites the underline stroke in the cell above.
When I reverse the order the cellstyle is applied (right to left, bottom to top, instead of left to right, top to bottom), the table above will be styled correctly, but other styles (e.g. if the style is "stroke-top") will not behave as I want..
Usually table cells will care about its own, but not on the other or adjacent cells, so there is no other option than re-applying the cell styles and even u can try out with the help of scripts.