Whatever you do to one repetition of a repeating field you should be able to do the same to a second repetition.
Can you describe the issue in more detail?
If you copy the contents of the date you entered in to repetition 1, can you paste it into repetition 2 without getting an error message?
In the lay-out mode the two repetions in the field are visible an have numbers (1 and 2).
But in browse mode I see only one, althoug in the settings I set it to show 2, vertically.
When I enter the first date, it's ok, but when I enter the second (after a space or "," or ";" or enter), whatever I try, I can not enter the second repetition.
Check your layout. Is there any chance that the second repetition extends even one pixel into a different layout part? If it looks tight, go into layout mode and try pulling down on the border between parts until there is obvious blank space between the part border and the bottom of the 2nd repetition. Now enter browse mode and test.
That was it. Problem solved. Thanks a lot!