Problem with breakpoints in Web Dynpro components

Hello experts,

I have problems with breakpoints in methods of Web Dynpro components. Sometimes everything works as expected and a new window with the debugger comes up. Sometimes the breakpoints are ignored, and debugging is impossible. It even happens that a colleague can debug and I can't or vice versa.

I am setting breakpoints with button "Set/Delete External Breakpoint", and the message always is "Breakpoint is set for user xxx". But sometimes when I display a method there is a warning that external debugging is not active. What does that mean and what is the reason for that?

As adviced in the SAP help document "Debugging Web Dynpro ABAP Applications" I have enabled the new Front-End Editor and the new debugger, but still the problem exists. Does anybody experience similar problems or have an explanation for this?

A second question concerns the different types of break points. My Web Dynpro component has an assistance class, and if I want to set a breakpoint there, I can choose between a session breakpoint and an external breakpoint. What exactly is the difference between these types? And here in the forum I sometimes read about internal breakpoints. Is this even a third type, or the same as session breakpoints?

Thanks, Karsten