This is reproduceable with m122.  
  
Open the attached document. Scroll to page 10 of the document.You will see 
that some headings have numbering and some do not. "Vorsätzliche und.." for 
example does not display any numbering, although it should. 
 
As "Vorsätzlich..." is heading 4, select it and double-click on heading 4 in 
the stylist, nothing will change in terms of numbering. Now double click on 
heading 1 and numbering will be displayed, then double-click on heading 4 
again and numbering will now also be displayed for heading 4. 
 
Now open the stylist and look at the properties for Heading 1 and Heading 4. 
In the Numbering Tab you see that "None" is selected as Numbering Style. 
Now go to Extras > Outline Numbering, when the dialogue has opened, just click 
OK. 
Try to assign a heading-style to the heading it did not work before, it will 
still not work for numbering. Yet the headings where numbering was displayed 
before will still display their numbering, even if you assign them to another 
style, they will not change it. 
 
Re-open the properties of the Heading 1 style and look at the numbering-tab. 
The selected Numbering-style is not "None" anymore but empty. The latter 
happened to all heading-styles! Go through all heading-styles and change them 
back to None. Now you will get the numbering displayed for all the headings. 
 
Concluding, one has to open the outline-numbering to get the numbering to work 
for those headings that do not display numbering, yet this will set all 
heading-styles to use an empty numbering-style, which has to be undone before 
numbering really works as expected. 
 
As the display numbering will work as expected after one has done the above 
and saved the document, this might be considered solved. Yet Extras > 
Outline-numbering setting all heading-styles to empty still happens. As a 
result the user has to undo that change every time after s/he has used the 
outline-numbering dialogue, which should not be necessary.