due to some kernel bug it happens sometimes on kvm machines that there is an incorrect reporting in steal time when using vmstat as can seen in the screenshot below

in that case zabbix will report a 100% steal time

when doing a cat /proc/stat there is not wrong reporting of steal time
i don't know how the agent looks for steal time ... vmstat ?

but it is in this case also reporting the wrong values as there is no steal time on the machine as can be seen in the other values.