I have only seen this with a flat file source, standard jdbc database tables only need the "Refresh/Reconnect Teiid Instance Connection" button to refresh and have previews work again.

Setup a Remote Server in JBDS
select Server externally managed
Remote and Remote Management Commands

• Create a new model project, add a File source
• Create a view model and do a preview on the view table

That works! Great.

Then:

• We right-click the server and press Stop. Then press Start
• Now when you try to preview again, it fails. The EAP server is in a reload-required state and the below error is shown in Designer log and a pop-up:
  !ENTRY org.teiid.designer.dqp.ui 4 0 2016-02-05 13:37:38.436
  !MESSAGE JBAS010473: Failed to load module for RA [org.jboss.teiid.resource-adapter.file]
  !STACK 0
  org.teiid.adminapi.AdminProcessingException: JBAS010473: Failed to load module for RA [org.jboss.teiid.resource-adapter.file]
  at org.teiid.runtime.client.admin.v8.Admin8Factory$ResultCallback.onFailure(Admin8Factory.java:202)
  at org.teiid.runtime.client.admin.v8.Admin8Factory$AdminImpl.cliCall(Admin8Factory.java:1591)
  at org.teiid.runtime.client.admin.v8.Admin8Factory$AdminImpl.addModuleResourceAdapter(Admin8Factory.java:397)
  at org.teiid.runtime.client.admin.v8.Admin8Factory$AdminImpl.createConnectionFactory(Admin8Factory.java:303)
  at org.teiid.runtime.client.admin.v8.Admin8Factory$AdminImpl.createDataSource(Admin8Factory.java:497)
  at org.teiid.runtime.client.admin.ExecutionAdmin.getOrCreateDataSource(ExecutionAdmin.java:373)
  at org.teiid.designer.runtime.TeiidServer.getOrCreateDataSource(TeiidServer.java:614)
  at org.teiid.designer.runtime.TeiidDataSourceFactory.createDataSource(TeiidDataSourceFactory.java:177)
  at org.teiid.designer.runtime.preview.PreviewManager.ensureConnectionInfoIsValid(PreviewManager.java:527)
  at org.teiid.designer.runtime.preview.PreviewManager.previewSetup(PreviewManager.java:1365)
  at org.teiid.designer.runtime.ui.preview.PreviewDataWorker$1.run(PreviewDataWorker.java:233)
  at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:119)

!ENTRY org.teiid.designer.ui 4 0 2016-02-05 13:37:38.863
!MESSAGE Error running preview. See log for more information.
!STACK 1
org.eclipse.core.runtime.CoreException: Error running preview. See log for more information.
at org.teiid.designer.ui.util.ErrorHandler.toCoreException(ErrorHandler.java:68)
at org.teiid.designer.ui.util.ErrorHandler.toExceptionDialog(ErrorHandler.java:106)
at org.teiid.designer.runtime.ui.preview.PreviewDataWorker.run(PreviewDataWorker.java:255)
at org.teiid.designer.runtime.ui.preview.PreviewTableDataContextAction.run(PreviewTableDataContextAction.java:99)
at org.eclipse.jface.action.Action.runWithEvent(Action.java:473)
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:595)
at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:511)
at org.eclipse.jface.action.ActionContributionItem$6.handleEvent(ActionContributionItem.java:462)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4481)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1329)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3819)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3430)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1127)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1018)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:156)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:654)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:598)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:139)
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:380)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:235)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:669)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:608)
at org.eclipse.equinox.launcher.Main.run(Main.java:1515)
at org.eclipse.equinox.launcher.Main.main(Main.java:1488)
Contains: * JBAS010473: Failed to load module for RA [org.jboss.teiid.resource-adapter.file]
!SUBENTRY 1 org.teiid.designer.ui 4 4 2016-02-05 13:37:38.864
!MESSAGE Error running preview. See log for more information.
!SUBENTRY 2 org.teiid.designer.ui 4 0 2016-02-05 13:37:38.864
!MESSAGE * JBAS010473: Failed to load module for RA [org.jboss.teiid.resource-adapter.file]

To fix it:

• We run a :reload on the EAP server with jboss-cli
• Then preview works again.

So, desired fix, when the server is in a reload-required state, reload the server or at least prompt for it instead of erroring out.