I think they are in alphabetical order (per color: bronze first, then silver, finally gold).
I don’t think it’s a bug that badges are ordered alphabetically. There are some other topics about cases where the alphabetical order does not lead to the best positioning, like Very teeny tiny minor issue with the default badge ordering & Badge order doesn't make sense.
I think you could change the order with CSS (Trust levels order exhibition in the badges page - #3 by awesomerobot) or use the suggestion to add numbers in front by customizing the text.