Hey, @sebastian_2430. Welcome to the Lightroom Community. I'll need more info to help you figure this out.
Please share the system info from Lightroom Help > System info > Copy and paste into a text document > Upload and attach here.
Has this started after recent Lightroom or OS updates? Does this happen when Lightroom is just launched, not in use, while using any tools, or after performing specific Develop operations such as AI Denoise, Enhance, Remove Tool, etc,?
Before going further, you must ensure all the data is backed up locally or in the cloud. You can log on to Lightroom Web (https://adobe.ly/3LUKpiM) to check and confirm everything is synced.
Thanks! Sameer K (Type '@' and type my name to mention me when you reply)