UNKNOWN host in alert mails

[steph42]

Hello,

Using zabbix in distributed mode.
Having problems with email alerts containing unkonwn hosts.

Receiving messages like the following:

Trigger: Disk I/O is overloaded on *UNKNOWN*
Trigger status: OK
Trigger severity: Warning
Trigger URL:

Item values:

1. *UNKNOWN* (*UNKNOWN*:*UNKNOWN*): *UNKNOWN*
2. *UNKNOWN* (*UNKNOWN*:*UNKNOWN*): *UNKNOWN*
3. *UNKNOWN* (*UNKNOWN*:*UNKNOWN*): *UNKNOWN*

Original event ID: 400000000086819


In the database the table events contains:
evientid | source | object | objectid | clock | value | acknowledged | ns
----------------------------------------------------------------------------------------------------
400000000086819 | 0 | 0 | 400400000014403 | 1417701390 | 0 | 0 | 245111389

What does objectid type of refers to in this case ?
Any idea about a solution ?

Thanks

[steph42]

precision

I must precise that in our distributed mode framework, several version of the agent are running.
Servers are running under zabbix 2.2.6 and 2.2.2.

Can it be a explanation ?