If you play a public match and switch between your support and the trapper this bug occurs. It has happened to me with Hank and Sunny, Hank’s screen becomes blue while Sunny has this cross.
Sunny’s has been reported before, consider yourself lucky, usually they flash violently. It seems to happen with people that have some sort of beam weapon in their kit and only on that weapon.
Also, changed title to better reflect the bug as it’s better known for what it does most