Hi Roland12,
Thank you for checking your browser's settings. I would have done the same thing.
We've actually seen similar cases, and it's indeed a weird behavior. I had a client yesterday with a related concern. Recently, his attachments to bills and POs are automatically downloaded while attachments to other transactions are previewed in a browser. I suggest contacting QBO Support to check this using more tools. That way, we can get to the bottom of this issue.
I'm just right here if you have additional questions.
