"Failed to load player data for 4a3d31ea-bc91-4d81-b246-3ebed946d022"

[frdmn]

Since I rewrote all of the "old-api-style" functions to work with the v2 API, my application center is properly and fully working again. Thanks for this :)

However, now whenever I request something via JSONAPI, I get some weird [WARN] Failed to load player data for XXX messages in the console.

Any ideas what this is?

I don't run my servers in offline mode. I also use the latest version of your plugin.

[d03n3rfr1tz3]

Mhh.. I had no idea, because I never saw this myself. But after a bit of googling it looks like it's a problem with your server playerdata. Tried to find a solution for you, but could not find a concrete one. But I can give you some hopefully helpful information.
https://www.google.de/search?q="Failed+to+load+player+data"&ie=utf-8&oe=utf-8

The problem is, that your server couldn't read one of the player NBT files. Looking into the Bukkit code, which should be similar to spigots, there are three possibilities:

1. file doesn't exist (if this really isn't checked by spigot before reading)
2. file is locked or otherwise not readable (permissions)
3. file is corrupt or not gzipped
   https://github.com/Bukkit/mc-dev/blob/master/net/minecraft/server/WorldNBTStorage.java#L197

You should check the file of that XXX-player. Maybe the player doesn't exists (anymore) or that player has problems with his/her progress (I guess).