CMS11: In use notification already exist error

Hi,

recently we have started to get a lot of "in use notification already exist" in our CMS11 episerver error logs. When this error occurs, our editors are unable to edit/save/publish content in episerver. We have been unable to find a solution since the error seems to be located within episerver (see error log)

We have noted that Optimizely has fixed a similar error in CMS12:

• CMS-2366 – Fixed an issue where when you tried to edit the same page from multiple tabs, In use notification already exists error message displayed in one of the editors. 

This problem makes it hard to work within episerver and we are wondering if there is a solution/fix/workaround for CMS11 ?

System.Web.HttpException (0x80004005): In use notification already exists.
   at EPiServer.Cms.Shell.UI.Rest.Internal.InUseNotificationStore.Post(InUseNotificationViewModelentity)
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContextcontrollerContext, ActionDescriptoractionDescriptor, IDictionary`2parameters)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c.<BeginInvokeSynchronousActionMethod>b__9_0(IAsyncResultasyncResult, ActionInvocationinnerInvokeState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResultasyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResultasyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_0.<InvokeActionMethodFilterAsynchronouslyRecursive>b__0()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResultasyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_6.<BeginInvokeAction>b__4()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_1.<BeginInvokeAction>b__1(IAsyncResultasyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResultasyncResult)
   at EPiServer.Shell.Services.Rest.RestControllerBase.EndExecute(IAsyncResultasyncResult)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStepstep)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStepstep, Boolean&completedSynchronously)