Sending time accuracy problem

when ever we are hitting fix gateway we are trying to capture all trades till that time.

that means :

if i hit gateway at 9:30 - i fetch all trades till 9:30 (100 let)

if i hit gateway at 10:30 - i fetch all trades till 10:30 (100 of 9:30+100 trads between 9:30 to 10:30 let)

and so on till 2:30

when trade volume increases 6500 then the following error occoures : " SendingTime accuracy problem "

NOTE :- clock is synchronized and NTP is working fine on both the server .