There is code that is very difficult to trace because of the interactions between the events it is called for and the debugger window. For example, if you want to trace code that is executed for "On display detail", you will notice that the very presence of the debugger window interferes with the actual display of the list form.

In those cases, please keep in mind that you can create your own process that displays a text interprocess variable and use that variable to display a log of the code. Of course this implies modifying your code to update that variable but it certainly is better than not being able to trace at all.