Steps taken (not sure if the error is reproducible with them):

• go to login page on mobile domain (this on huwiki)
• leave it there for a long time
• try to log in (results in session timeout error, as expected)
• log in again + get through 2FA

Resulted in an error message The provided authentication token is either expired or invalid, with the login actually being successful. This seems unwarranted in the first place (why did it not refresh the token after my failed login attempt? also exactly what failed here, since I was logged in successfully?) but more importantly it is a completely unhelpful error message (there is nothing else on the page, about how to fix).