[Gameplay] Dragon soul on 5th dragon killed

So I finished a game about an hour ago that my team get the dragon soul buff only after the 5th dragon killed of my team, and is interested in why this happen. One thing to note is I play on Taiwan server but there isn't a official forum so I would like to share my story here. Heres an Imgur link of all the 6 dragons in this game. (Sorry for the in-game Chinese text ) 1st dragon: Ocean @8min 2nd dragon: Fire @14min (Opposite team got it) 3rd dragon: Earth @20min 4th dragon: Earth @25min 5th dragon: Earth @31min 6th dragon: Earth @37min (When we finally get the dragon soul,which can be seen at shaco's status bar)

I have searched the internet about this bug, and the only result I got is a youtube video with 1 view only. We both have a shaco in the team, and with the weird game announcement on the 1st dragon, I guess shaco's clone killing the dragon may be the reason of this bug. Another thing is that the map didn't change into Mountainous Rift as well after the 2nd dragon died, and only did so after the 3rd one died.

I hope someone can look into this bug as it is so rare and weird at the same time.