Seems like a related problem:
http://illustrator.uservoice.com/forums/601447/suggestions/50633909

It just started happening, might be an OS update or Adobe update. But it is happening in more than one file. I will open some older things to see if older version files do the same thing. I might try a beta version if yall have it out.

Yes, I can see this at your screenshots, but not within the file... and if there is no difference between GPU and CPU Preview, it probably means it just struggles with rendering in general. The GPU is integrated in the iMac’s M3 chip, AFAIK...
I’ll try to bring some attention to it. Have you ever noticed this with other files at all?

Hi there,
I will attach more samples, see how the shadow is showing on one shape, but the same thing one board over just stops rendering like halfway? And some of them don't show any at all? Yes, the shadow still shows in the appearance panel, but not on the object. If I change the color, the shadow shows up. If I change to GPU, no difference.
Odd, I dont know why the clipping mask is a grouped circle, but even if I unmask the images, its still showing it as a black block. It only renders it if I embed the image or reopen the file. Sorry yes the two with grey circles are just empty for now.

Thanks for the file, studying it.

So far all the shadow applied to all rectangles seem to be rendered fine for me (although I’m at Windows 10, with a different GPU).
When a shadow vanishes like this — does the effect still get shown in Appearance panel? Does it appear back if you toggle View > Preview on CPU?

Two circles missing images (Francium and Radium) are not clip groups when I study them in Layers... no images are there. I noticed though that those clip groups that do have images are made of a grouped ellipse and an image — never heard of it being a problem, but perhaps clipping an image with a grouped ellipse can lead to images vanishing? Are you sure you had the images for these two elements in the first place? Odd...

Alos, just wanted to mention the atomic weight for Francium has parentheses (while others elements don’t), and the Sodium’s rectangle has smaller corner radii than other elements.

If you can, please try to check how the file behaves in Beta build — it’s available in your CCD app and will get installed next to the general build (be warned though that it will rewrite your .ai file association).

Try this file package, but it is happening in more than one file for me. Its been happening in a lot of files since a recent update. I dont know if its the OS or the Adobe version causing the problem.
2023 iMac, Apple M3, 26.0.1,

https://museumartsinc-my.sharepoint.com/:f:/g/personal/davidknapp_museumarts_net/En3k2p2Co8xGpwW0TKJjgr0BItQ5w83qYsQXW4APF_qfMQ?e=JmHBUk

David, please share a test file (with images included, using File > Package), and the spec of your computer: OS, GPU, etc.