Created attachment 86691 [details]
Source for object used to reproduce the issue

Copying an object from an older PowerPoint file into a current .odp document works initially. The object can be ungrouped into its original lines, shapes etc. The object correctly displays when you hit F5 for Slide Show. The object can be grouped with other objects to form a larger diagram.

However, after you save, close and re-open the file, the object may not look the same and is no longer selectable for editing. When you hit F5, it is not displayed in the Slide Show.

The only way to get rid of the offending object in the background is to copy the remaining useable parts of the slide to a new slide and then delete the slide with the offending object.

When you group the offending object into a larger diagram, the entire diagram becomes un-editable and part of the background. I have have had to redo 2 large diagrams because of this issue.

The good news is that I have figured out one such object where this issue happens on demand, every time. To reproduce the issue, do the following:

1) Take a look at the attached file Zener_Diode.jpg. This picture shows the object that will be used in the next steps.
2) Open the attached file Symbols.ppt
3) Locate the Zener Diode object, which is in the 6'th row down, 2'nd column over
4) Select and copy the Zener Diode object into a new slide in a new .odp document
5) Hit F5 for Slide Show, verify the Zener Diode displays correctly
6) Now exit the Slide Show, save, close and reopen the .odp file
7) You will now see that the the Zener Diode object is missing the horizontal line with the right angle lines
8) Hit F5 for Slide Show, you will not see the Zener Diode at all. Exit the Slide Show
9) Try to select the Zener Diode object. You can't!
10) The only way to delete the Zener Diode is to delete the entire slide.
My sample file demonstrating the issue is attached, see Bug_Report.odp