F5 NTPD sync failed with NTP servers. But the servers are reachable and we can see it on tcpdump

Hi Guys, i want to ask if any of you has experienced this issue with NTPd not syncing with ntp servers. The servers and F5 are exchanging NTP requests and responses. But the ntpq- np shows that the server is unreachable. I tried to find if there are any known cosmetic issues on version 11.3 HF4 but i cannot find anything. ive already restarted the NTPD service but still got the same issue.

Note: The NTP servers are reachable via TMM interface. Management subnet have no routes going to the ntp servers. I already added static route on the TMM interface going to the ntp servers.

I normally fix NTP problems with these commands:

bigstart stop ntpd
ntpdate 
bigstart start ntpd

There is also this bug:

What output does ntpdate gives?

ntpdate

Sometimes the initial time difference is too great to automatically synced by ntpd. Then you first need to get it in sync by using ntpdate.