Known Issues & Limitations
Jira Labels
1. Deleted labels are still suggested in label field
Sometimes deleted labels might be still suggested as recent labels. This is caused by Jira storing recently used labels in browser local storage. There is a ticket to fix this in Jira Issue tracker.
In the meantime, you can delete the local storage data from your browser. To do that, open Console → Application (or Storage in Firefox) → Local Storage. After that, find your Jira URL, right click and use Delete All popup to delete temporary data stored in your browser.
2. Field 'labels' cannot be set. It is not on the appropriate screen, or unknown
When editing and deleting labels, sometimes you might get this error.

Error message when labels field is not editable
This happens when label is not in Create or Edit Screen. You can add labels field to those screen, and it should work as expected.
You can find screens from Project Settings → Issues → Screens.

Add labels field to Jira screens
3. Zero issue count (empty labels)
App might show labels with zero issue count. These labels are from archived projects, please refer to docs below:
Manage Labels from Archived Projects
4. Delayed operation (Labels not deleted/updated immediately)
There are cases when you delete a label, the deleted label is not removed from the app. This is due to a caching issue with Atlassian’s API that we use in some of the application’s features. Please refresh the table periodically to see the update.
Colorful Custom Labels
1. Board in team managed projects
Boards in team-managed projects (e.g. work management), service and product discovery projects are very limited and do not support adding custom fields.
Colorful Labels is a custom field, therefore currently it cannot be added to board view. There is a ticket in Jira backlog to track this limitation.