Hello there!
Is it possible that, while I can check the stats of all my players, one player is "idle"?
With this I mean that when I click on his name nothing happens. Literally nothing. The background of the name blinks and that's all.
Also, the same player do not appear in the players list using the permission manager.
I am really puzzled and I'd appreciate any suggestion you might give! :-/

Not sure, really. Could be some oddball issue with the way I tried to improve performance.. I'll try and have a peek when I have time

Thank you so much! Ask me whatever you might need for that, in case

It should be clickable so you are able to ban them, in case they log off after doing something you didn't like ;)

Something really odd is going on: as I explained, that player seems to be "invisible" to your plugin.
2 days ago he logged in (of course I didn't mentioned this issue), we had a seemingly friendly chat and at that point I noticed that, while he being alive and online, I could click on his name and see his stats.
After a while he logged off and I can still click his name and check his things (as I can do to all the other offline players), as I guess it should be the normal behaviour.

I am really baffled because I am 100% I didn't touched any config file or any player permission in the meanwhile so I really don't know what is going on.