REST API endpoint (Get user default columns) returns incorrect columns with duplicate custom fields

Issue Summary

REST API endpoint (Get user default columns) returns incorrect columns with duplicate custom fields

Steps to Reproduce

1. Create two Next-gen projects, each having a custom field of the same name, say Custom01. Alternatively, create one Next-gen project with its own custom field having the same name as one already existing.
2. Run a JQL search (e.g. project = <Next-gen project 1>). Go to Columns->My Defaults and ensure the Custom01 column is checked. Export the output as XML or CSV (all fields).
3. Execute the Jira REST API endpoint: Get user default columns

Expected Results

• The Custom01 column returned by the Jira REST API endpoint should match the one in the exported XML or CSV file.

Actual Results

• The Custom01 column returned by the Jira REST API endpoint may be one or the other duplicated field.

Workaround

Rename one (or more) of the duplicated custom fields so that their names are unique.