AdvancedHMI has been designed to work optimally using multiple forms with a driver instance on each form. As a form is hidden, the driver is set to DisableSubscriptions which effectively pauses updating for the hidden form.
When using TabControl, you have only one form with a single driver, therefore all controls are updated even when hidden. To work around this, you must create a driver for every tab you have and set the ComComponent property for the associated tab's controls to it's driver instance. Then using code, you need to set DisableSubscriptions to True when the tab is hidden, then back to False when it becomes visible again.
Something like this:
Private Sub TabControl1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles TabControl1.SelectedIndexChanged
If TabControl1.SelectedIndex = 0 Then
Tab1Driver.DisableSubscriptions = False
Tab2Driver.DisableSubscriptions = True
ElseIf TabControl1.SelectedIndex = 1 Then
Tab1Driver.DisableSubscriptions = True
Tab2Driver.DisableSubscriptions = False
End If
End Sub