Diagrams are not displayed when containing page is exported as PDF

What i did:

• Create New Empty Page
• Add Diagram Macro to Page (with Empty Reference)
• Save Page
• On The Page, click Export -> Export as PDF

Expected Result:
The generated PDF includes the diagram

Actual Result:
The generated PDF only includes the link to the diagram (see attachment)

I set up a brand new wiki (also version 8.4.5, on my local machine running Windows 10) and tried to reproduce the issue there but I couldn't. On my new wiki the export works fine.

On another wiki that I set up for one of our customers the export produced the (rather useless) file in the attachment.

I've looked through the logs but couldn't find anything that seemed to be related to the issue.

I'm not really sure if this is a bug but I'm clueless how to track down this issue.

I would be glad if someone could give me a hint.