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,
Some Poskim prohibit Yichud in an elevator. However, the opinion of most Poskim is that it is permitted as long as the elevator may be stopped on any floor by those wishing to enter. This would apply in office and apartment buildings and other public buildings during the day and early hours of the night. However, late at night or very early in the morning, one should be stringent. It is certainly a middas chassidus to avoid Yichud in an elevator wherever possible.
(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