21 + 9 X 10 = 300 -9 = 291 feet. That's not counting how far down the hallway the switch is from the elevator, or slack loops. You're really close to the limit. You can go over the limit(you shouldn't), but you're running into degraded signal territory. If you can get your hands on a fluke linkrunner you'll be able to test the cables for shorts, crosses and total length. They're not cheap, but they're worth it.
Also something to look at, from what I've seen from elevator shafts, your cables are probably in the same bundle of wire as the car's electric supply cables. That long of a run next to ac lines is probably inducing quite a bit of voltage and noise into your data cables. If it was up to me, I'd install fiber media converters on the car and the top of the shaft. That will get rid of your length problem and electrical noise problem.