log monitoring trigers from old string

[hbm]

I have a log monitoring setup , it works as expected ,however it triggers randomly looking for the same string from previous dates ,some times year long.
Item
----------
Name: XXXlogmon
Type: Zabbix agent (active)
Key: log[/hhh/hhh/hhh/diag.log]
Type of infromation: Log

Trigger
---------
Name {$XXX_GROUP}DiagLog /hhh/hhh/hhh/diag.log No Space for Log: XYZ
Severity Minor
{Template-Name:log[/hhh/hhh/hhh/diag.log].iregexp(XYZ_NO_SPACE_FOR_LOG)}=1

So it triggers some times getting the string fro old dates ...

Any help for solution would be greatly appreciated .

Thanks