a lot of devices are pingable but zabbix knows those as problem

[mhsnsd]

Hi everyone
I had problem on some of my devices and zabbix-server couldn't ping those devices, so zabbix knew them as problem.
but after resolving problem, those device are in problem list still, zabbix can ping them but them appears on list
anyone could help me?

[superlava]

Have you verified utilization of unreachable Pollers?