Is there a problem of Yichud in the elevator?
(especially considering there's a possibility that the elevator may get stuck)
[and specifically those without cameras]
Quoting from this website,
(See the link for sources.)
The shiur yichud is longer than an elevator ride, so it shouldn't be a problem. See this site which has a short discussion of it: http://koltorah.org/ravj/The%20Yichud%20Prohibition%20-%20Part%202.htm