Hero defence buff shield icon missing

I encountered a small graphics glitch, missing defence buff shield icon. I had Magni on my attack team. I fired Magni’s special and immediately activated a turtle banner, before Magni’s attack animation had ended. After the attack animation had finished, Magni and the adjacent heroes were missing the shield icon. The shield icon was visible on the two other heroes. According to the hero stats, the defence buff from the turtle banner was active, only the icon was missing.