ASUS RT-AC66U Fimrware 380.57 VPN Password

[Stovine]

Hi,
My Router is ASUS RT-AC66U with Merline Fimrware 380.57
I created few VPN account and password week ago, everything works fine

until today, some strange things happned
I have existing VPN user
VPNuser1 Pass1
VPNuser2 Pass2
VPNuser3 Pass3

i want to change the VPNuser1's password, so click delete button, and put VPNuser1 as username with new password, click add button, after that my VPN user list became
VPNuser2 Pass2VPNuser2
VPNuser3 Pass3VPNuser3
VPNuser1 NewPass1

so system automatically append the user name to existing password. i did not notice that since VPNuser2 complaint that he can not connect anymore, so i tried to reset his password back,

i click delete button for VPNuser2 and put back VPNuser2's password and click add, now the VPN user list became
VPNuser3 Pass3VPNuser3VPNuser3
VPNuser1 NewPass1VPNuser1
VPNuser2 Pass2

how can i modify the password for existing user without effect outer users?
i found if i add a brand new user name, that will not happen.

thanks for any help

 

[Stovine]

Update:
I did delete the user and click apply, then i can add user without affect other user's setting.