Listener is not catching update event

[J Manas Kumar]

Hi guys 

I am facing one bizarre issue.

I created one listener which will be start to work means which will initialize when I update a specific custom field which is label type.name ex :-  Impacted Apps

I have a job which push data into the label field.

Now once it's get updated then my listener will be trigger for update event I had set.

Once the Impacted apps should get update from job response, then it will update another 2 label field called lb1 and lb2.

 sometimes it's happening but sometimes it's not updating the other two fields.

I dont understand why?

Any clue ?