We're using Zabbix version 3.0.11 and have a character item "healthString". To check its value there is the following trigger:
So if none of the latest 10 values matches the regular expression the trigger is fired. Unfortunately there are some values which should match the RegEx but nevertheless the trigger is fired.
I verified the RegEx with different tools and also with the test function at the global regular expression page in the frontend. The result was always that the value matches the RegEx.
So I think there is an error with the RegEx evaluation.