event-alarm-error ?

I've got some problems with the event alarm feature of OWS 7.22. I have written an event handler and set the onconfig paramter correctly as I can see from online.log. Also, I can see from online.log that my event handler is sometimes (it depends on the event class) called by: /bin/sh -c event-handler ... ,which works well, and sometimes by: /bin/sh /bin/sh -c event-handler ... ,which does not seem to work because my event handler doesn't make anything. Who can help me? Is this different calling maybe a bug in informix ? Thanks in advance, Pascal