What you were expecting to happen, and what actually happened:
Should be able to see the Bronze Elite Medal on the troop card like you can for Gold & Silver Elite Medal troops. There is no visual difference between a Bronze Elite Medal troop and a troop that has no Elite Medals.
How often does this happen? When did it begin happening?
Every time you view any troop that has been upgraded to the Bronze Elite Level. Started after I updated the game to 7.0
Steps to make it happen again
View a troop that has the Bronze Elite Level.
You will see in the screenshots I have attached that the troop has been upgraded to Bronze Elite Level but there is no Bronze Medal on the troop card.
More than visual. Kinda pertinent when deciding which kingdom needs which medall troops for power levels. Like 10 silver, I display troops, and can instantly find which bronze ones to level up as an example.