As I know, you can't break an axis, but maybe you can fix your problem as follow:
1- With the icon "AXIS LINE" create a second axis. Now you have 2 axis (AXIS_1 and AXIS_2)
2- CLick on AXIS_1, Press CTRL key while selecting the axis end point above the dimension text and drag it...
You could clean your CATPart or CATProduct with the CATIA V5 cleaner (CATDUA.exe), after you will have to load your part or product and after your CATDrawing.