short:
Tables, vertical lines white (in front), horizontal lines in black (in the back)
after undefined cause: horiziontal in front, vertical in the back.
Workaround: click (in top menue) on the white color again (for the vertical lines)

describe:
There is some serious complications with vertical table lines! I want to have the vertical lines cut out of the horizontal ones. This is easy, with doing white vertical table-lines. Works perfekt. But sometimes, not always to reproduce, there is a trouble, where the white lines, hide behind the black herizontal ones after copy&paste or changes in the layout. There is not really a special case where it always happen, it just happen unexpecting. The quick solution ist to mark the table, only pick the vertical line in the top menue, click on the line-color icon (where already white is choosen) and choose white again. Normaly, nothing should change, but then all things are correct again. Seems definitly like a bug.
Can you please take a look on this behavior?