Steps to reproduce:

We see 10m to 1hr time lag in graphs after upgrading to 4.0.16. We are using 1 proxy server with 2k servers monitoring. 

FYI, h/w clock and system clock are in sync with ntp and same with DB server.

Configurations...

#cat abbix_server.conf

LogFile=/var/log/zabbix_server.log
DebugLevel=3
PidFile=/var/tmp/zabbix_server.pid
DBHost=********
DBName=****
DBUser=****
DBPassword=******
StartPollers=64
StartPollersUnreachable=10
StartPingers=10
StartHTTPPollers=20
CacheSize=256M
HistoryCacheSize=128M
TrendCacheSize=32M
ValueCacheSize=256M
Timeout=30
AlertScriptsPath=/opt/zabbix/lib/alertscripts
ExternalScripts=/opt/zabbix/lib/externalscripts
SSHKeyLocation=/home/build/.ssh
StartPreprocessors=10
StartTrappers=10
StartDBSyncers=10
Timeout=4
LogSlowQueries=3000
StartProxyPollers=5
StatsAllowedIP=::/0

#cat zabbix_proxy.conf

Server=*******
Hostname=zbx_proxy
ListenPort=10055
LogFile=/tmp/zabbix_proxy.log
DBName=****
DBUser=****
DBPassword=****
ConfigFrequency=5
DataSenderFrequency=1
StartPollers=64
StartPollersUnreachable=10
StartHTTPPollers=30
CacheSize=256M
StartDBSyncers=20
HistoryCacheSize=256M
Timeout=30
ExternalScripts=/opt/zabbix/lib/externalscripts
LogSlowQueries=3000

Any help would be highly appreciated.