How to reproduce: Check the attached project and video

Workaround: force an update in the MapElement
Public Class RadForm1

    Private bingKey As String = ""
    Dim myTimer As Timer
    Public Sub New()

        InitializeComponent()
        Dim bingProvider As BingRestMapProvider = New Telerik.WinControls.UI.BingRestMapProvider()
        bingProvider.UseSession = True
        bingProvider.BingKey = bingKey

        AddHandler bingProvider.SearchCompleted, AddressOf bingProvider_SearchCompleted

        Me.RadMap1.Providers.Add(bingProvider)

        myTimer = New Timer
        myTimer.Interval = 500
        AddHandler myTimer.Tick, AddressOf OnMyyTimerTick
    End Sub

    Private Function OnMyyTimerTick() As Object
        myTimer.Stop()
        Me.RadMap1.MapElement.InvalidateMeasure(True)
    End Function

    Private Sub bingProvider_SearchCompleted(sender As Object, e As SearchCompletedEventArgs)

        myTimer.Start()

    End Sub
End Class