Problem in editing a symbol


I have problem in “editing” a symbol as below:

  1. Double click the symbol from the library window.
  2. The symbol then appear on the stage.
  3. Import an image (e.g. .jpg) to the stage. Therefore the symbol has a new look!
  4. Save the file.

The edit symbol worked normally. However when I closed and re-open the file, other symbols will be changed to the edit symbol, some symbols seems to be disappear…

What may be the problem? I think the problem may come from step 3.

Thanks and best regards