Target selection problems

Sometimes in a battle, I cannot select the toon that I want to attack. In the picture below, I could not select Royal Guard as a target for my B2. It looks like there should be no problem, but there was. I tapped the entire area on and around RG, but he was unselectable. I could select STH and Lando without trouble.
It's possible that it only happens when K-2SO is present and buffed, I'm not certain of this.
https://s4.postimg.org/85cyw7dkt/Heroes_2017_02_27_16_32_02.png