DNS Load Balancing (Issue with Round Robin Algorithm)

Hi

I’m having some issues with DNS-Load Balncing. I’m using Thunder 3030s (ADC) right now and i’m on a beginner level. The configurations are quite simple (L-4).
We need to load balance Port-53 Queries between 2 Real Servers. The issue that i’m having is that, when the VIP is hit. The request terminates on both Real Servers at a same time inspite of ROUND ROBIN STRICT or ROUND ROBIN Algorithm.

Following are the current configurations. It would be great if i can get some guidance concerning to this.

\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*
interface ethernet 1  (\*\*Towards Internet\*\*)

enable
  ip address 10.10.10.252 255.255.255.0
!
!
ip route 0.0.0.0 /0 10.10.10.1
!
health monitor tcp
  method tcp port 53
!
health monitor udp
  method udp port 53
!
slb server internal-server 10.10.10.254
  health-check ping
  port 53 tcp
  port 53 udp
!
slb server server 212.249.200.135
  health-check ping
  port 53 tcp
  port 53 udp
!

slb service-group service-tcp tcp
  method round-robin-strict

health-check ping
  member internal-server 53
  member server 53
!

slb service-group service-udp udp
  method round-robin-strict

health-check ping
  member internal-server 53
  member server 53

!
slb virtual-server DNS-vip 10.10.10.233
  port 53 dns-udp
    name UDP
    source-nat auto
    service-group service-udp
  port 53 dns-tcp
    name TCP
    source-nat auto

    service-group service-tcp
\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*

Thanks.

i am also suffering from the same issue when i test DNS(VIP) using nslookup
against single query 4 hits/connection are established on VIP.
I dont exactly know the issue right now. Why the VIP is getting 4 HITS against 1-single NSLOOKUP Query.