problem

Using the DEL or Backspace key removes the whole content instead of deleting only single characters.

reproduction

1. Import the attached task.
2. Edit one of the segment without target content (segmentNrInTask > 3)
3. Type a text "Das ist das Haus"
4. try to use backspace 4 times to delete the last word

Always on the second key press of backspace the whole segment content is deleted.

The same happens with the DEL key.