Illustrator changes colors and/or displays the document as empty

Hello everyone,

We've been experiencing the following problem with Adobe Illustrator for the past days:

• After opening an existing document, some colors are displayed incorrectly. For example, a spot color (which consists of 100% magenta) suddenly appears as a “dirty black.” This doesn’t happen only with the same spot color, but with different spot colors as well. In addition, white (0/0/0/0) is also displayed as “dirty black.”
• In some other documents, the file appears empty after opening, and you only see the actual content when switching to outline view. We do not have overprint preview or similar options turned on. If I change the file extension from .ai to .pdf and open it in Acrobat, I can see the content again. However, the colors also appear as “dirty black” in Acrobat instead of, for example, magenta.

The problem does not occur for all employees on the same document, even though we are all working with Illustrator 29.8.2 (it also happens with version 29.1, for example). We also use different OS versions (14.5, 15.1.1, 14.6.1, 26.1, etc.), and even with different systems the problem may appear—or the document may open normally.

Unfortunately, I cannot share a document here because it contains sensitive customer data. Has anyone experienced similar issues or found a solution?

Thanks in advance and best regards,
Marleen