The values should be typed in separate lines. 
The submitted values however become one line with "
" instead of
linebreaks.

For example:
"Option 1
Option 2
Option 3"

becomes
"Option 1
Option 2
Option 3"

I fixed this issue temporarily for me by changing
   $tmp = explode("\n", $seloptions);
to
   $tmp = explode("
", $seloptions);
in action.addprop.php