It doesn't happen often but did happen 2 times this week.
I get stuck while flying in the vanish mode. I can't move anymore.
I can't teleport anywhere. Even after killing myself I can not move anymore.
The only thing that helps is reconnecting.
I find myself under the map then and die.

Sounds like you have the vanish.permenant perkission granted to yourself.

Checked it.
It's not granted.

Merged post

Can't be granted anyway cause I use it by command.