Migration component webdynpro: Component is not yet ready to be converted

Question

I'm using NWDS v7.31 and migrate the component in webdynpro application. On Cheat sheets - the Delete Implementation Coding from Interface Controller step, I have an error message:

Unhandled event loop exception

ObjectNotModifiableException: Attempt to modify read-only object: //WebDynpro/Controller:com.pwc.bc.registration.wd.parnr.approval.comp.PartnerNumberApprovalCompInterface!
    at com.sap.ide.metamodel.core.DevelopmentObjectProxy._prepareForModify(DevelopmentObjectProxy.java:465)
    at com.sap.ide.metamodel.webdynpro.implementation.AppClassProxy.setCodeBody(AppClassProxy.java:668)
    at com.sap.ide.webdynpro.componentmigration.internal.actions.DeleteInterfaceControllerImplementationCodingAction.run(DeleteInterfaceControllerImplementationCodingAction.java:23)
    at org.eclipse.ui.internal.cheatsheets.ActionRunner.runAction(ActionRunner.java:86)
    at org.eclipse.ui.internal.cheatsheets.data.Action.execute(Action.java:100)
    at org.eclipse.ui.internal.cheatsheets.views.CoreItem.runExecutable(CoreItem.java:497)
    at org.eclipse.ui.internal.cheatsheets.views.CoreItem.runExecutable(CoreItem.java:492)
    at org.eclipse.ui.internal.cheatsheets.views.CheatSheetViewer.runPerformExecutable(CheatSheetViewer.java:1044)
    at org.eclipse.ui.internal.cheatsheets.views.CoreItem$1.linkActivated(CoreItem.java:89)
    at org.eclipse.ui.forms.widgets.AbstractHyperlink.handleActivate(AbstractHyperlink.java:233)
    at org.eclipse.ui.forms.widgets.ImageHyperlink.handleActivate(ImageHyperlink.java:199)
    at org.eclipse.ui.forms.widgets.AbstractHyperlink.handleMouseUp(AbstractHyperlink.java:327)
    at org.eclipse.ui.forms.widgets.AbstractHyperlink.access$2(AbstractHyperlink.java:311)
    at org.eclipse.ui.forms.widgets.AbstractHyperlink$4.handleEvent(AbstractHyperlink.java:125)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3910)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3503)
    at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2405)
    at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2369)
    at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2221)
    at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:493)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:194)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1311)

Then, I uncheck read-only on folder properties and try again. But I still get an error message on Start migration step on Cheat sheets:

Cannot start migration

Component 'com.pwc.bc.registration.wd.ao.approval.comp.AOApprovalComponent' is not yet ready to be converted. Check the migration Cheat Sheet again to find out what needs to be changed.

Please help me to review it and give me your thoughts.

Thanks,