Urgent: Seemingly random crash when switching Widget's | Invocation related, presumably

Hello there,

I can’t wrap my head around this crash that haunts our app consistently but never replicate-able. Our UI is managed solely through Blueprints. When switching between Widgets, every now and then the following (see below) crash occurs, and we have absolutely no idea where to start. Our application is hitting the pre-release stage, however we do not want to ship nor present the application to our clients with the this issue lingering around, so any advice or idea on how to solve this issue would be very appreciated. I know what I do not provide enough in-depth assets to specify the exact reason for the crash but any starting point would be a huge help as well.

I am not responsible for the UI implementation, therefore I do not know the exact procedures right before the crash, however a call with the visual scriptwriter told me that the crash does not relate 1:1 to destroying or creating new widgets. In our latest instance of the crash, the only thing done was changing the index of a widget switcher. Making it likely that the issue is buried deeper within the UE4 Kismet Library. We are using a VR environment (Oculus), however, based on the call-stack I do not think this is related to the crash.

Following is the crash-log (attachements)

So what I can read from the crash log is that UE4 is trying to handle the player input events and calls the responding callbacks - My guess is that it tries to invoke an event within a widget that is no longer existent.