What you were expecting to happen, and what actually happened?
Unit couldn’t use his spell, resulting in endless game
What are the steps to make it happen again?
Skip, for now.
Do you have any screenshots or video you want to share with us so we can see the problem? Attach them to your post!
here is a youtube video, friend’s stream broadcast recorded on my laptop. MUTE the video, my cooling fan was making ridiculous noise.
Did the Paladin target enemies correctly before this occurred?
@Nimhain bro its the same as i posted here, but in revese.
Cant target Mercy with spell :(
Game acts like it sees the first unit as alive. Aka ghost unit 
I dunno, when my friend asked me to see, he game was already like this. I wanted to record more, but he got bored and ended the game -.-
As i was watching, he paladin casted spell like 10 times, missing every single time. I will ask him about previous casts and let you know.
EDIT: Yes, paladin killed other 3 units properly.