The actions to show the forward/backward history list include the text of the lines. But, this text is always extracted from the current buffer of the edit pane, which is not necessarily the buffer of the history position. In many case, the history position may be on a line that is outside the range of the current buffer, in which case an exception is thrown and no history is shown.
The problem is in the CellRenderer of NavHistoryPopup. Rather than finding the buffer of the history path, it just uses the current buffer of the edit pane.
Shlomy, what version or revision of Navigator did you see this in?
Latest main trunk version , 15546 I think.
I see the problem, it's fixed in revision 15547.