SRV for failsafe

Hi,

SETUP:

EXCHANGE 2013 = MBX+CAS

CERTIFICATE= LICENCED

2 WAN IP (SETUP WITH FAILSAFE MODE- AUTOSWITCHOVER INTERNALLY)

Issue:

I created 2 SRV records on public dns: ( FOR FAIL OVER)

_autodiscover._tcp.zerobit.ru.        IN    SRV    1    0    443    mx01.company.com

_autodiscover._tcp.zerobit.ru.        IN    SRV    100    0    443    mx02.company.com 

mx01.zerobit.ru.        IN    A    WANIP 01     
mx02.zerobit.ru.        IN    A    WANIP 02 

When i run the Testconnectivity through Microsoft:

Autodiscover fails once in 3 times: During failure I see that the srv autodiscover is accessing mx02.

My goal: Is automatic failover when our mx01.company.com goes down.

Please advise me where I have done wrong.