I found a bug.
Minecraft Server 1.12.2
While we are in nether portal, we cannot use a keyboard. If server have a user authentication, for example via flexiblelogin plugin – user must type /login password when it connecting to server. But user is in nether portal! Keyboard is locked. User cannot type password! In admin console I can teleport user to nearby place typing a command “/tp user x y z”. Buf flexiblelogin plugin lock user coordinates, command does not work on unlogged users.
How to unlock keyboard while user is in portal to nether?