I know this happen at this time.
https://community.playfab.com/questions/28816/leaderboard-error.html
I will update about PVP Rank Contents.
but It ruined.
Only Just 1000 users get correct rank
(Brendan said but this is not sure I think because I saw wrong rank in 1000)
So if provide correct rank is so heavy, then please provide percentile.(Top 10%, 20% etc)
current system is ridiculous. and deceive the users.
Please consider updating this feature.