I have hosts with a template with external check item. It seems that the proxy is executing the script even though the host is unavailable in Zabbix. This can cause an issue since the script steps have to time out before an exception is thrown. Across a large number of hosts in this state, there are a lot of script instances waiting to time out.

It appears this occurred when I first added the host on 8/3/2020 (host has been unavailabe since it was added), then each time I made a change to the template that contains the external check (8/4/2020, 8/11/2020)

Server = Zabbix 5.0.1 (docker container image)
Proxy = Zabbix 5.0.1 (docker container image)
FE = Zabbix 5.0.1 (docker container image)