Cannot access to secondary x axes

[a.straw]

I have a chart with 3 series (xy), 2 of them with primary axes and the
third with secondary axes.
I have in Graphic/Options/Axes both primary and secondary X and Y
selected, I have a good chart but I can only access to the title of
the secondary X axes.
If I go to the graph toolbar and look in the chart objects list, I
have (same order9 : primary X axe, primary Y axe, secondary Y axe,
legend, primary X axe title, primary Y axe title, secondary X title,
secondary Y title.
The secondary title is there, but not the axe itself. I cannot click
on it to get the properties.
Any solution ?
Thanks