This doesn’t feel like a bug, unfortunately it feels more like they changed the minimum requirement and just implemented it poorly, likely in a hurry to meet the ow2 launch.
The new requirement appears to be Master+ however rather than preventing people below the mark from entering the leaderboard (like how the diamond limit was implemented), they just wipe everyone below Masters periodically.
Welp good news is Blizzard support finally acknowledged that this is a bug in two of my ticket responses. Bad news is we still have no idea when the devs will fix it. I linked my post with with those ticket responses if you want to read them here:
I didn’t fight through hell and make it to top 500 by losing hope. I for one will be patient and wait as long as it takes for them to give me what I earned.
I’ve updated my post with more information again. Season 36 Missing Top 500 Rewards At the bottom is my comprehensive list of all the posts about top 500 bugs I could find. It is probably incomplete and inaccurate so suggestions on corrections are welcome. And as always, if you have not already, please create your own post if you have these issues so that I can add it to the list and have these issues resolved.