Newline in Lists and table cells not correctly saved after WYSIWYG editing

The WYSIWYG editor does not handle newline (using Shift-Return) correctly.

Trying to insert a newline into a list element: After saving, the whole list element is lost.

Trying to insert a new line into text contained in a table cell: The newlines are not stored. Looking into the wiki markup, the lines content is written back-to-back into one line.