i was battling someone, and i was using a flygon that had a +1 boost to speed and attack by use of dragon dance, a guy switched in a slurpuff that had a sitrus berry, at full health, and unburden apparently had activated without using up the berry as he outsped my +1 flygon.
his slurpuff was adamant, as was my flygon, and at +1 flygon can outspeed the likes of jolteon, and even mega mewtwo. but his slurpuff went first

I'm having difficulty recreating this, the Flygon is always outspeeding Slurpuff, even without +1 speed. Is there anything else you can think of that may factor in?

Closing due to age. If this is still happening, please make a new ticket!