Hi Jan,
When your application has been upgraded with several versions, your database structure changes as well. When you upgrade several tines with the Built-in database being update and the external database not, you will face synchronization issues when you decide to change your database 3 Mendix updates later.
The best way is to delete your current external database that causes the error and create a new empty external database. Use this as your new database and Mendix will synchronize all the domain model configurations to your new external database.
Hi Jan,
When I get a M2EE error it is usually a different service or program already using the 8080 port. Disable the service or program using it, or you can change the port in App > Settings and edit the configuration.
In App explorer go to the app > settings then edit or create new configuration and on the server tab edit the runtime and admin port to 8081 and 8091.