When moving a client from one group to another, the entire list of clients will disappear. Refreshing the page makes the clients reappear. This issue only happens when logged in with the default "admin" account.
This issue has been fixed in SEP 14.0.
FIX ID: 3897026
Symptom: Moving a client from the default group to a different group in Symantec Endpoint Protection Manager causes the rest of the clients in the default group list to disappear.
Solution: Added check to ensure that every time a table column is moved, it can be rendered properly.
Reference: New fixes and component versions in Endpoint Protection 14