Shift-del sometimes not cutting highlighted text

1. put "text" in the clipboard, for example (assuming you are using windows) by
   1. pressing <windows>-r
   2. enter text
   3. press <shift>-<pos1> (marking "text")
   4. press <ctrl>-c (to copy "text" to the clipboard"
2. create a new page
3. enter "a title" <enter>
4. enter "foo" <enter>
5. enter "bar" <enter>
6. enter "blub"
7. press <shift>-<up> <shift>-<up> (marking "blub" and "bar")
8. press <shift>-<del> (cutting the marked region)
9. press <shift>-<ins>

Observe that "text" was pasted resulting in "footext".

Expected: three lines with "foo", "bar" and "blub"