While generating Plan's CSV export some values of "User Picker" custom field(-s) are not included

Issue Summary

In case you have a custom field of "User Picker" type added to Advanced Roadmaps for Jira plan then under some circumstances the values of this field will not be included in generated Plan's CSV export.

This is reproducible on Data Center: (yes)

Steps to Reproduce

Below found steps and test scenarios allow us to more-or-less constantly replicate the reported problems. However, even for these steps, we could see some fluctuation between test attempts (some users are constantly added, some not). Therefore the exact pattern of why some custom field ("User Picker") values are always added and others are not is not clear yet.

Preparation steps:

1. Create a new project, 3-4 issues, 3-4 users, “User Picker” custom field.
2. Create a new plan and add a custom field to the plan.
3. Assign values to the “User Picker” custom field, save changes and export data to CSV
   • Only “Jira Admin” (system administrator account created during installation) is added to export
     

Page refresh behaviour:

1. Add the “Assignee” field to the plan (I have added it since it is also a “User Picker” type)
   • Export to CSV: same as before (sometimes “Jira Admin” is removed — the test doesn’t give constant results)
2. Add assignee values and save changes
   • Export to CSV: all expected values are correctly exported
     
3. Removed assignees and save changes
   • Export to CSV: all expected values are correctly exported
     
4. Refresh the page without doing any changes
   • No values for the custom field are added to exported CSV. Please note that this test step's results are not constant. Sometimes only “Jira Admin” (system administrator account created during installation) is added to export
     

Test with "Team":

1. Create a Team and add all users there
   • Export to CSV: only some values are added to export
     
     
2. Refresh the page without doing any changes
   • Export to CSV: all values (only members of the Team) are added to export
     
3. Delete Team
   • Export to CSV: No values for the custom fields are added to exported CSV. Please note that this test step's results are not constant. Sometimes only “Jira Admin” (system administrator account created during installation) is added to export

Expected Results

Generated CSV export should include all appropriate values of the custom fields that are available in the current Plan

Actual Results

While generating Plan's CSV export some values of the "User Picker" custom field(-s) are not included

Workaround

Currently, there is no known workaround for this behaviour. A workaround will be added here when available