Instead of silently disabling item zabbix should store the error message (may be in separate table). This error message should be available somewhere in web gui for monitoring operators, because as of now it requires digging into server logs which operators don't have normally. The item value should be shown as "NOT_SUPPORTED" (or alike)

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21331:20111108:185817.876 Item [s:push_check.sh[/etc/zabbix/externalscripts/id_rsa user@s deluge_download_speed.sh]] error: Type of received value [ERROR: SSH key: '192.168.2.3' does not exist] is not suitable for value type [Numeric (unsigned)]
21345:20111108:185821.510 Item [s:push_check.sh[/etc/zabbix/externalscripts/id_rsa user@s deluge_download_speed.sh]] became not supported: Type of received value [ERROR: SSH key: '192.168.2.3' does not exist] is not suitable for value type [Numeric (unsigned)]
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