Exception on project import

I Export a project using
project.Export(filename, ProjectDictionaryOption.ResolveReferences, ExportOption.None, ProjectExportOperationFlags.Standard);
After that, i delete the projekt and try to import it with
mApp.Folders.Projects.Import(filename);
EB throws an error, see the attached screenshot.
After that the operation fails with the exeption:
Message: Systemfehler bei der VBA-Integration!

Server stack trace:
bei Aucotec.EngineeringBase.Interop.IAucProjectsFolder.Import(String FileName)
bei Aucotec.EngineeringBase.Client.RuntimeHostAdapter.ProjectsFolderHostAdapterViewToContract.Import(String filePath)
bei System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Object[]& outArgs)
bei System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg)

Exception rethrown at [0]:
bei System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
bei System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
bei Aucotec.EngineeringBase.Client.RuntimeContract.IProjectsFolder.Import(String filePath)
bei Aucotec.EngineeringBase.Client.RuntimeAddInAdapter.ProjectsFolderAddInAdapterContractToView.Import(String filePath)
bei xxxxx.xxxxx.ImportProject(String filename)