Steps to reproduce:

1. Create an item with Type=Calculated and Formula=

   last("system.cpu.util[all,idle,avg1]")+last("system.cpu.util[all,nice,avg1]")+last("system.cpu.util[all,user,avg1]")+last("system.cpu.util[all,system,avg1]")+last("system.cpu.util[all,iowait,avg1]")+last("system.cpu.util[all,interrupt,avg1]")+last("system.cpu.util[all,softirq,avg1]")+last("system.cpu.util[all,steal,avg1]")+last("system.cpu.util[all,guest,avg1]")+last("system.cpu.util[all,guest_nice,avg1]")
   

   (After ZBX-10710 is resolved, the last two terms should be removed.)

2. Create the ten used items with keys system.cpu.util[all,...,avg1] and Type=Zabbix agent or Zabbix agent (active). The problem is relevant for both active and passive agents.
3. Wait for some minutes and observe the resulting graph of the Calculated item.

Result:
See the attached 100%jagged.png screenshot. The sum of values is not 100% (although in source code they are calculated as ratios of their sum).
My items were set to update at 27 second intervals, but that should not be important.
Expected:
The sum of state values should be a constant 100%, a straight line.
This discovery was inspired by ZBX-11174.