Hi,
We have a custom field which is not being used in any Screen but still being used in different Jira Issues and Project.
Please refer to the screenshot below:

We have a custom field Union Affiliation which is not used in any screen but when we search using filter we get 8291 issues where this field is being used and this number is increasing continuously.

The strange thing is we cannot see the custom field on the screen of any project/issues but able to find custom field in search (JQL).
Not sure how to figure it out as it is being updated in background.