CustomFieldManager returns null for a custom field

[Chandramouli Vashisth]

Hi All,

I am trying to fetch custom field from plugin by using : 

customFieldManager.getCustomFieldObjectsByName(FIELD_NAME);

 Sometime it is able to fetch the custom field object but sometime it is not able to fetch the object.

When It is not able to fetch the object, then I have to disable and enable the plugin and  it will start to work.

Can anyone let me know what can be the permanent solution to it.

Thanks,

Chandramouli