NTP Time Difference between Active and Passive Nodes

Hello,

I need some help. I have a two F5 (Active- Passive) and they are configured to have same NTP server. Active one is showing correct time, however the standby is showing 3 minutes of difference compare to the Active appliance. Even I sync the time manually, it slowly experience delay, and time difference start getting increased between both of the appliances.

Because of the 3 minutes differences, when I tried to sync the devices I get an warning saying that:

System Times of Devices Do Not Match One or more system times of the devices in the device trust do not match the system time of the local device. 

Auto or manual device group sync operations may fail. Verify that the NTP Settings on all devices are properly configured and that the system times are equal. 

/Common/f5-01 is 3 seconds ahead.

I have tried to query the ntp server from both appliance but that didn't work. According to result of Ntpq -np, both devices can reach and take time from NTP.

Is there anyone have the same problem before?

Thank you.