This problem can occur if you use two or more RenderWindows and make an interaction in one instance that also modifies the scene in another instance.
The RenderWindow in which the interaction takes place is always correct as VTK forces a re-render of the scene.
The second RenderWindow is not correctly updated unless the interaction somehow triggers a ForceImmediateUpdate. Normally only UpdateRequests are put into the EventLoop. As soon as this Eventloop is processed, the rendering is updated.
The problem is, that User-Input-Events have a higher priority when processing the Eventloop.
For fast interactions this means that many input-events (e.g. mousemove) are handled before the rendering is updated.
This can be seen in the ExtApp when the cross position is moved by clicking into a RenderWindow (in the default layout of StdMultiWidget) and moving the mouse. When the mouse is moved slowly the rendering-event are processed because there are relatively few input-events.
When the interacion is fast (fast mouse movement) there are too many input-events and the rendering is not correctly updated -> the user interacts but does not see any update in the RenderWindows.
This problem could be solved by calling ExecutePendingRequests() on all relevant RenderingManagers (in MITK there should be only one static instance in use). This makes sure that all pending rendering requests are correctly processed before new user-input events are handled.