sysmessages table issue
This is the expected behavior for system compatibility views from SQL Server 2012+:
When referenced in a user database, system tables which were announced as deprecated in SQL Server 2000 (such as syslanguages or syscacheobjects), are now bound to the back-compatibility view in the sys schema. Since the SQL Server 2000 system tables have been deprecated for multiple versions, this change is not considered a breaking change.
Example: If a user creates a user-table called syslanguages in a user-database, in SQL Server 2008, the statement SELECT * from dbo.syslanguages; in that database would return the values from the user table. Beginning in SQL Server 2012, this practice will return data from the system view sys.syslanguages.
You're probably going to have to fix your database to not use the same names as deprecated system tables (now system views in the sys
schema).