It's clearly visible as non-completed on Guardian, but there are at the same time three Conquests listed as completed under the Season Conquest tab. I even have the completing of Cursed Peat on video, with over 400 kills and the conquest popping as completed for us all..
I also completed GR75, The Thrill and Cursed Peat - in that order if it helps with the troubleshooting.
Extremely annoying. I hope Blizzard fixes this asap.
/Prisse (Hope IS the last thing to abandon us they say...)