Cross check the association properties Common_Observe
Here are some possible XAS errors in Mendix and how to fix them:
Object of type 'System.XASInstance' cannot be updated: This error occurs when an object no longer exists but is still being tried to be updated. To fix this, you can:
Manually delete the records in the association table
Use microflows or an overview page for a sys admin
Avoid using the database manager to manage data in the database