If you rebind your zipline button, it's possible to get into the "on zipline" state without actually being on it, by activating ethereal shift and then getting on the zipline. The only things you can do in this state is activate zipline boost (which doesn't do anything because you are not actually on a zipline) or get out of it by jumping or crouching. This isn't gamebreaking or anything, since the player can easily fix it, but it is stil annoying.