I've just started having a problem with the eyedropper tool in InDesign. When I select an object and then use the eyedropper tool to fill the selected object with a new color from my document, the selected object disappears. I have no idea why it's doing this or how to stop it.
Although I didn't take exact note, I think this might have coincided with the 2023 macOS update to Sonoma.
Yes, screen issues is a known problem on Sonoma. InDesign doesn't officially support Sonoma yet (you can search the forum for Sonoma for more info). Try to enable GPU Performance in Preferences or/and hide rulers. It helped many users. Otherwise, you can revert to Ventura.