Hey, @Kathrin38307846rkn6. Welcome to the Photoshop Community. I'll need more info to help you figure this out. Please share the system info from Photoshop Help > System info > Copy & paste into a text document > upload & attach here.
Before troubleshooting, ensure you're working on Photoshop v25.9.1 & the latest version of Windows.
Reverse the Technology Preview for 2016 GPU & try this:
Create a mask on the Artboard level & check if that helps.

Let me know how it goes.
Thanks!
Sameer K
(Use '@mention' to tag me when you reply)