I just ran into a problem with one of my AnimNotifys firing 2 times when it should have just fired once. It turns out when you use the “Manage Notifies” notify manager and rename one of them, that one will no longer work right. I’m running UE 4.26
First obviously you must delete the AnimNotify in your AnimBP because for some reason it doesn’t auto rename it. Next add what the new one is named, one would think this is all that is needed, Wrong. lol
Because I renamed the AnimNotify in the “Manage Notifies” notify manager the old one was somehow still linked and firing even though it was renamed and the old named one was gone. (Because it was renamed lol)
I decided to just save everything and close the project down, then I restarted my project and guess what? everything works like it should.
I just wanted others to know about this bug. I tried to figure out how to submit a bug report around here but since the new lame updated junky barely usable forum, I have no idea where to submit this bug or even look. AnswerHub is read only now too LMFAO (btw the optional tags for posts here are useless when you can’t put your own in there)
UPDATE:
I thought it was fixed but it just started firing the AnimNotify twice again, lol back at trying to figure this out 
LATEST UPDATE:
Found this on AnswerHub and it solved my problem! (IsServer branch to the anim notify BP is what fixed it for me)
"Yoyo -
So, I had this issue and found a fix. I definitely made the change in the blendspace to favor the highest weighted. I did not do anything funky with the weights as it didn’t appear to affect the problem.
What I eventually found is that the animation was playing on both the server and client, which was causing the anim notify to double up and get called twice, producing two sounds. I added a simple IsServer branch to the anim notify BP and then ignored the client notify, letting the server one through to fire the multicast sounds.
Works like a charm. Hope it helps!"