So while I was working on our sandbox environment to update our customization to version 9. I found maybe a bug in the related entity views. See the screenshot what I mean exactly. But the screen stays blank, it works in the Classic interface though. Other OOB entitites like Invoices, Opportunities work.
Does anyone know if this is a know bug or just an limitation?
(I did clean my browser cache.)
Just want to be sure before I let Microsoft call me and try to explain this to 3 support engineers.