Guide below will effective only in case your AI file is easily damaged,
otherwise refer to topics below, which contain a lot various ways of solving
https://www.openfiletool.com/aiopen.html AI Open File Tool
Copy artwork from a damaged file into a new file
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.