The nominal service ceiling on all CRJ series is 41,000 but they rarely attain that due to weight. Some larger airliners are certified to 43,000 and a few private jets (G550 etc.) can go as high as 51,000.

59k is complete BS.

Flightaware is usually reliable although there are occasional reporting anomalies. If your flight's track shows 29k consistently then that's what it was.