Hello everyone,
This is my first time posting on this forum, despite the hundreds of times it was suggested in the lectures 
Anyway, I’ve come to suggest a change on the video which might cause issues for people going through the lessons on newer engine versions.
In the BlueprintImplentableEvent video, the Event Graph Bluepring structure suggested by Ben is as such below.
The issue with this structure that I came to find after about 5 hours of debugging is that the BP Aiming Comp. Reference is set after it is added to the viewport.
What this does is it attempts to add the PlayerUI BP to the view port, but the BP Aiming Reference has not been set yet. The issue become apparent when the viewport attempts to get the Aiming Component Reference to get the RoundsLeft variable. However, since the BP Aiming Component Reference hasn’t been set, it can’t get the “RoundsLeft” variable and it returns “None” the first time through. The next step is to set the BP Aiming Reference so it will work as intended after it is set.
After figuring out what was wrong, the fix was simple. Just change the structure so that the BP Aiming Reference is set right before it is added to the viewport. This way, the BP Aiming Reference is set so the RoundsLeft variable is accessible before it is added to the viewport.
The error I received was this.
The only difference between receiving this error and not receiving it was changing the structures as mentioned above.
For what ever reason, the Get Aim Point Color and Opacity binding is unaffected by this change and works regardless if the BP Aiming Comp Reference was set before or after adding to the viewport. I assume that this has to do with the fact that RoundsLeft is an UPROPERTY variable. However, I am not too sure.
I hope this prevents a lot of headaches for you out there. I learned a lot in the 5 hours it took so if you come across any issues, be sure to grind them out so you have a better understanding of how things work.