In T24215 the new display action broadcast class was used inside the StdMultiWidget. This involved connecting the display action events. The QmitkAbstractMultiWidget provided either a set of synchronized or non-synchronized display action event functions.
The original StdMultiWidget used a mixture of synchronized and non-synchronized functions (see mitkDisplayInteractor).
For the multi widgets to work as expected, each multi widget has to decide on its own, which action functions it wants to connect.