Hello,
i have weird issue with monitoring our switches with SNMP. For example i have interface Ethernet1 monitored by item with type SNMPv2 agent and update interval 60 seconds. Details you can see on attached screenshot.
Problem is, there are duplicated data for Port-channel1 (and for all items). like this:

2017-03-31 15:39:21 11628422976
2017-03-31 15:39:19 13456456632
2017-03-31 15:38:20 12580544272 # why is there data item just one second after previous
2017-03-31 15:38:19 13681267800
2017-03-31 15:37:20 15787583032
2017-03-31 15:37:19 14110371632
2017-03-31 15:36:20 0 # why is there zero?
2017-03-31 15:36:19 13036400376
2017-03-31 15:35:20 26326772720

I tried reproduce this behavior with other snmp tools like snmpwalk or Telegraf SNMP input but i seems to be Zabbix related issue.