Two broker triggers for same document

Hello All,

I am facing some issues with broker triggers. I have created two triggers. One is serial and the another one is concurrent with max execution thread 5. Both triggers are in different servers. If I am publishing the document from one server, ideally what should happen? document should subscribed by both the triggers. But What is happening in my case is sometimes the document subscribed by both the triggers and sometimes not. And all the time the document is subscribed by the concurent trigger. But only sometimes by serial trigger.

Can any tell the reason why the document is not always subs by the serial trigger?

Should I need to change any property of the document?

Thanks for clarification this!!