Software

Illustrator Repair Toolbox- https://www.repairtoolbox.com/illustratorrepair.html
1. Open the damaged file, and then choose Object > Path > Cleanup to remove unwanted items (for example, stray points, unpainted objects, empty text paths) from the artwork.
2. If the original file contains multiple layers, choose Paste Remembers Layers from the Layers Panel (CS3) or Palette (CS2) pop-up menu to ensure the artwork appears on the same layers when you paste it into the new file.
3. Using the Selection tool, drag a marquee around the artwork.
4. Choose Edit > Copy.
5. Choose File > New to create a new file.
6. In the new file, choose Edit > Paste In Front to paste the artwork in the correct position on the page.
7. Choose File > Save.

If the new file exhibits the same behavior, it may contain a damaged object. To determine whether an object is damaged, delete it from the new file, and then save and reopen the file and try to re-create the problem. Repeat for each object in the file.
When you can no longer re-create the problem, delete and re-create the damaged object in the original file:

* If an Illustrator-drawn object is damaged, then re-create the object with the drawing tools in Illustrator.
* If a linked image is damaged, then re-create the original image, and then replace it in your artwork.
* If a text object is damaged, then convert the text object to outlines or change its font.

To quickly change all fonts in a document:
1. Open the document in Illustrator and Choose Object > Unlock All.
2. Choose Edit > Select All.
3. Choose Type > Font, and select a font not currently used in the document.

Note: To prevent text objects from becoming damaged in the future, reinstall the problematic font from the original disk.