Got someone else's PvP rewards
A few players have reported getting guardian progress instead of their actual class when using elite specs. Were you playing as Daredevil? (see https://forum-en.gw2archive.eu/forum/support/bugs/So-my-Reaper-is-a-Guardian-apparently/first#post5774561)
As for getting a second burst of reward track progress, are you sure that wasn’t just the animation replaying? When you go to the reward track panel at the end of a match, it always initially displays your progress from before the match and then plays the animation of your reward being added. You can view the panel multiple times, and see the animation replay each time, which could be mistaken for receiving progress more than once.
That makes sense; I was on my Daredevil. The reward track issue was likely just the animation as you said.
Thanks!