Test Studio Crushes on Element edit

[04.09 11:24:25,Telerik.TestStudio.exe(16060:1),Error] App.LogUnhandledException() : EXCEPTION! (see below)
     Situation: Unhandled exception!
     Outer Exception Type: System.InvalidOperationException
     Message: Collection was modified; enumeration operation may not execute.
     HRESULT: 0x80131509 (Official ID (if app.) = COR_E_INVALIDOPERATION, Error Bit = FAILED, Facility = FACILITY_URT, Code = 5385)
     Call Stack:
          at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
          at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
          at System.Collections.Generic.List`1.Enumerator.MoveNext()
          at ArtOfTest.WebAii.Design.UI.ElementExplorer.Models.ElementNodeViewModel.RemoveNotRelatedNodes(ElementNodeViewModel parent)
          at ArtOfTest.WebAii.Design.UI.ElementExplorer.Models.ElementNodeViewModel.RemoveChild(LightElementNode elementNode)
          at ArtOfTest.WebAii.Design.UI.ElementExplorer.Models.ElementNodeViewModel.Children_CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
          at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
          at Telerik.Windows.Data.RadObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
          at System.Collections.ObjectModel.ObservableCollection`1.RemoveItem(Int32 index)
          at Telerik.Windows.Data.RadObservableCollection`1.RemoveItem(Int32 index)
          at ArtOfTest.WebAii.Design.ProjectModel.ObservableList`1.<>c__DisplayClass9.<RemoveItem>b__8()
          at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
          at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

[04.09 11:24:27,Telerik.TestStudio.exe(16060:1),Error] App.LogUnhandledException() : EXCEPTION! (see below)
     Situation: Unhandled exception!
     Outer Exception Type: System.InvalidOperationException
     Message: Collection was modified; enumeration operation may not execute.
     HRESULT: 0x80131509 (Official ID (if app.) = COR_E_INVALIDOPERATION, Error Bit = FAILED, Facility = FACILITY_URT, Code = 5385)
     Call Stack:
          at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
          at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
          at System.Collections.Generic.List`1.Enumerator.MoveNext()
          at ArtOfTest.WebAii.Design.UI.ElementExplorer.Models.ElementNodeViewModel.RemoveNotRelatedNodes(ElementNodeViewModel parent)
          at ArtOfTest.WebAii.Design.UI.ElementExplorer.Models.ElementNodeViewModel.RemoveChild(LightElementNode elementNode)
          at ArtOfTest.WebAii.Design.UI.ElementExplorer.Models.ElementNodeViewModel.Children_CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
          at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
          at Telerik.Windows.Data.RadObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
          at System.Collections.ObjectModel.ObservableCollection`1.RemoveItem(Int32 index)
          at Telerik.Windows.Data.RadObservableCollection`1.RemoveItem(Int32 index)
          at ArtOfTest.WebAii.Design.ProjectModel.ObservableList`1.<>c__DisplayClass9.<RemoveItem>b__8()
          at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
          at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

[04.09 11:24:27,Telerik.TestStudio.exe(16060:1),Framework] Manager.get_ActiveBrowser() : The current ActiveBrowser is either invisible or disconnected.