Visio Plan - Strange Issues

Hello All,

This is a bit convoluted so I'll try and keep this as succinct as possible.  Ask away if you need more info.

• I have created a network rack elevation diagram in Visio
• I used Visio stencils from several different manufacturers
• I needed to edit some of the Visio shapes that I used.  I did this by
  • Right-clicking the shape
  • Under Group, clicking on "Open stencil name"
  • Clicking the shape and ungrouping it
  • Making my changes as needed
  • Ctrl-A to select every part of the shape
  • Grouping everything back together
  • Closing the shape
• I save my work frequently, including immediately before closing the drawing or the application
• To this point, everything works and looks as expected
• But then:
  • If I close the file or close Visio, and reopen my drawing, 
    • Every shape I edited is messed up in one way or another
  • If I save the file as a DWG or DXF and open it in CAD
    • Entire shapes are missing, or
    • Elements or parts of shapes are missing
  • If I save the file as a PDF
    • 8 out of 10 times it's perfect, but
    • 2 out of 10 times it exhibits some of the issues described above

This is work-related and a few of us are mystified as to what is going on here.  My employer is an O365 shop and all of our software is licensed.  I am running all of the latest O365 updates.

I'm happy to provide additional info, screenshots, etc. so please just ask.

Thanks in advance for any assistance.

BG