I have the same issue and use 8.6 version. Is there any solution?
Dear Serdar,
From the screenshot it is difficult to understand what is going on. The issue indicates that the database has an issue, however, for more details we would need to check it via a Service Request.
Please submit a service request and then, one of our support engineers can help you in detail: https://apps.bentley.com/srmanager/ProductSupport
We have lately made many improvements in the material data structure in CONNECT Edition V22. Which version are you using?