Except kepler, other versions such as Mars, Luna, Neon have the same problem.

!ENTRY org.eclipse.graphiti.ui 4 0 2018-07-10 15:03:36.727
!MESSAGE GFCommandStack.execute(Command) java.lang.ClassCastException: org.eclipse.bpmn2.impl.ExpressionImpl incompatible with org.eclipse.bpmn2.FormalExpression
!STACK 0
java.lang.ClassCastException: org.eclipse.bpmn2.impl.ExpressionImpl incompatible with org.eclipse.bpmn2.FormalExpression
at org.eclipse.bpmn2.modeler.ui.property.tasks.IoParameterMappingColumn.getTargetExpression(IoParameterMappingColumn.java:108)
at org.eclipse.bpmn2.modeler.ui.property.tasks.IoParameterMappingColumn.getText(IoParameterMappingColumn.java:80)
at org.eclipse.bpmn2.modeler.runtime.jboss.jbpm5.property.JbpmTaskDetailComposite$DataInputOutputEditor.getText(JbpmTaskDetailComposite.java:91)
at org.eclipse.bpmn2.modeler.core.merrimac.dialogs.TextObjectEditor.createControl(TextObjectEditor.java:115)
at org.eclipse.bpmn2.modeler.core.merrimac.dialogs.TextAndButtonObjectEditor.createControl(TextAndButtonObjectEditor.java:58)
at org.eclipse.bpmn2.modeler.core.merrimac.dialogs.ObjectEditor.createControl(ObjectEditor.java:99)
at org.eclipse.bpmn2.modeler.runtime.jboss.jbpm5.property.JbpmTaskDetailComposite.createInputParameterBindings(JbpmTaskDetailComposite.java:224)
at org.eclipse.bpmn2.modeler.runtime.jboss.jbpm5.property.JbpmTaskDetailComposite.createBindings(JbpmTaskDetailComposite.java:146)
at org.eclipse.bpmn2.modeler.runtime.jboss.jbpm5.property.JbpmUserTaskDetailComposite.createBindings(JbpmUserTaskDetailComposite.java:44)
at org.eclipse.bpmn2.modeler.core.merrimac.clad.AbstractDetailComposite.setBusinessObject(AbstractDetailComposite.java:131)
at org.eclipse.bpmn2.modeler.core.merrimac.clad.DefaultDialogComposite.setData(DefaultDialogComposite.java:224)
at org.eclipse.bpmn2.modeler.core.merrimac.dialogs.AbstractObjectEditingDialog.aboutToOpen(AbstractObjectEditingDialog.java:190)
at org.eclipse.bpmn2.modeler.core.merrimac.dialogs.AbstractObjectEditingDialog.open(AbstractObjectEditingDialog.java:258)
at org.eclipse.bpmn2.modeler.core.merrimac.dialogs.ObjectEditingDialog.open(ObjectEditingDialog.java:75)
at org.eclipse.bpmn2.modeler.core.features.ShowPropertiesFeature.execute(ShowPropertiesFeature.java:92)
at org.eclipse.graphiti.features.custom.AbstractCustomFeature.execute(AbstractCustomFeature.java:83)
at org.eclipse.graphiti.internal.command.GenericFeatureCommandWithContext.execute(GenericFeatureCommandWithContext.java:64)
at org.eclipse.graphiti.ui.internal.command.GefCommandWrapper.execute(GefCommandWrapper.java:51)
at org.eclipse.graphiti.ui.internal.editor.EmfOnGefCommand.execute(EmfOnGefCommand.java:54)
at org.eclipse.graphiti.internal.command.GFPreparableCommand2.doExecute(GFPreparableCommand2.java:43)
at org.eclipse.emf.transaction.RecordingCommand.execute(RecordingCommand.java:135)
at org.eclipse.emf.workspace.EMFCommandOperation.doExecute(EMFCommandOperation.java:119)
at org.eclipse.emf.workspace.AbstractEMFOperation.execute(AbstractEMFOperation.java:150)
at org.eclipse.core.commands.operations.DefaultOperationHistory.execute(DefaultOperationHistory.java:488)
at org.eclipse.emf.workspace.impl.WorkspaceCommandStackImpl.doExecute(WorkspaceCommandStackImpl.java:208)
at org.eclipse.emf.transaction.impl.AbstractTransactionalCommandStack.execute(AbstractTransactionalCommandStack.java:165)
at org.eclipse.graphiti.ui.internal.editor.GFWorkspaceCommandStackImpl.execute(GFWorkspaceCommandStackImpl.java:97)
at org.eclipse.graphiti.ui.internal.editor.GFCommandStack.execute(GFCommandStack.java:138)
at org.eclipse.graphiti.ui.internal.parts.ShapeEditPart.performRequest(ShapeEditPart.java:575)
at org.eclipse.gef.tools.SelectEditPartTracker.performOpen(SelectEditPartTracker.java:194)
at org.eclipse.gef.tools.SelectEditPartTracker.handleDoubleClick(SelectEditPartTracker.java:137)
at org.eclipse.gef.tools.AbstractTool.mouseDoubleClick(AbstractTool.java:1069)
at org.eclipse.gef.tools.SelectionTool.mouseDoubleClick(SelectionTool.java:527)
at org.eclipse.gef.EditDomain.mouseDoubleClick(EditDomain.java:231)
at org.eclipse.gef.ui.parts.DomainEventDispatcher.dispatchMouseDoubleClicked(DomainEventDispatcher.java:291)
at org.eclipse.draw2d.LightweightSystem$EventHandler.mouseDoubleClick(LightweightSystem.java:518)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:197)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4418)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1079)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4236)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3824)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1121)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1022)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:150)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:693)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:610)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:138)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:388)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:90)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55)
at java.lang.reflect.Method.invoke(Method.java:508)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:673)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:610)
at org.eclipse.equinox.launcher.Main.run(Main.java:1519)