This usually happens when other Wazers also report alerts at or near the same location. Because of this, the app merges the alerts, and the most recently reported type is the one that appears on the screen.
Another situation is that when passing by a “Construction” site, the app “asks” if there is a lane closure? When the user(s) report the respective lane closure, the alert changes from “Construction” to “Lane closed”!
This happened to me too: I requested the inclusion of a construction alert on a Federal Highway and when passing by the spot it had changed to “Left lane closed”!