Your mount may normally perform just fine. Then while you are doing a two star alignment with calibration stars, the mount is way off when performing a goto to one of the calibration stars. Or the list of stars presented for alignment or calibration does not make sense for the time of the night or time of year.
This is a rare bug in the programming of the Nexstar and NexStar+ hand controls. It also affects NexRemote. It is believed to be caused by a corrupted variable in the hand control memory. It can occur only once or twice a year during regular use or perhaps more frequently.
Celestron programmers have not yet tracked down the cause of this problem. However, it can be cured for a particular instance by doing a factory reset. This clears the corrupted value from the memory.
To do a factory reset, press MENU and then scroll to the UTILITIES submenu. Press Enter, and then scroll to the FACTORY SETTINGS option. Follow the instructions including cycling (turning off then turning on) your mount.