some users in SEPM console switch to user mode

Dear All,
 
I am having this issue for some time but never gave importance since things were working fine
Some days back I noticed that when I moved a particular client which was in user mode to another group i did see there were about 10 more entries with the name as same different logon user /computer, different ip and different mac
If i had to right click or delete one of the user n switch him ti computer mode all the other users disappear from the group and its fine with only the few users which r in computer mode
if I change the group and open the group again same things happen that is I see the 10 more entries again
I am using 12.1.1 MP1
appreciate your kind help
 
regards
 
simon