When you use 802.1x authentications, the access point regularly requests re-authentication. During re-authentication, the communication is disconnected temporarily and reconnected again even if it is in the middle of scanning.
Under normal circumstances, the reconnection process is fast and it should not affect the data communication. However, certain types of wireless access point take longer to complete the re-authentication. In such case, it may result in communication error and thus stopping the scanning process.
Try scanning again.
If this phenomenon occurs frequently, extend the intervals (Session-Timeout) for requesting re-authentication in the wireless access point or RADIUS Server.