As you probably know by now, the problem was an entity called 'Activity'. A parameter of a Java action in the databasereplication module is also called 'Activity'. Having a parameter and an entity with the same name can lead to problems in the Java code. Therefore, the Modeler renamed the parameter to 'ActivityParameter1' but the user code still depended on 'Activity'.
It is good practice to let Java parameter names start with a lower-case character. This will avoid problems like these and it is in line with normal Java conventions. The databasereplication (which you imported) does not respect this convention and this caused the problem.
We accepted your ticket and will try to come up with a good solution for a future version of Mendix.
It seems like the database replication module which is build in version 3.2.1. is giving the errors. Submit a ticket to Mendix regarding this module and request a 4.1. version of the module? Some deprecated (in 4.1.0) java code is being used in the 3.2.1. version?