Iterator.OnBubbleEvent help

We are getting a frequent error in various applications that we have been unable to pinpoint.  It seems simliar to but the post doesn't specify how it was fixed.  Can anyone help clarify how this error would happen so we can find where it is happening?

Object reference not set to an instance of an object.

   at OutSystems.HubEdition.WebWidgets.Iterator.OnBubbleEvent(Object sender, EventArgs args)

   at System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args)

Note: We are still using 9.0 but working on our upgrade to 10.

Hi Rebecca, 

In version 9.1 we've changed the behavior of the Notify widget to run all callbacks on server side (to be more efficient). 

This change broke components like the "Event System" that was making use of an internal and unsupported API we changed during the project.

If you are getting these errors without calling any internal API and you are not using these unsupported components, you may have found a bug in the new implementation. It would be great if you could isolate the problem in a simple example so that we can look at it.

Just a quick final note. Our change wasn't supposed to break any old behavior because we added a new action and left the old one as deprecated.

best regards,