In addition to what is suggesting, do look into the events, I think that its the event thats is causing this issue.
I was unable to open your project, but from what you have described, it looks like the event is not setup properly. The place where you are calling the event to the place where the event is executed is not working. I would focus on troubleshooting the event setup.
You also might need to bind the event like in the picture:
Thanks