Asunto: [BUG] "Double promotion" error message

When trying to promote a player from my Junie squad, I get the "Error: double promotion" message. However, the player remains at my junior school with the option to be promoted, and he doesn't exist in my main squad.

This is the link to promote him, with what I believe to be his ID, in case of helps in tracing the problem:

https://sokker.org/juniors/action/Promote/juniorID/27294055

tried to log out / in?

It didn't help, but it eventually worked again, without me really doing anything :-?

You have to log off, not close tab (if You do so) just log off with use of the button in top right corner

might not work for smartphones (I am just not sure) but you might also try logging in using private/incognito mode
if You want to avoid it entirely I would suggest not ticking 'remember me' box on log on (I think it is the reason of these inconveniences)