Hi Malte_Bittkau1 ,
Based on the above information, If it's a reproducible issue. Since community support engineers no longer have direct access to the PG team for feedback. I would suggest opening a Support Ticket. The Ticket Engineer will assist you in investigating the issue and report it to the product team
If you are a Power BI Pro or Fabric licensee, you can create a support ticket for free and a dedicated Microsoft engineer will come to solve the problem for you.
It would be great if you continue to share in this issue to help others with similar problems after you know the root cause or solution.
The link of Power BI Support: Support | Microsoft Power BI
For how to create a support ticket, please refer to How to create a support ticket in Power BI - Microsoft Power BI Community
Best Regards,
Community Support Team _ Caitlyn