Problem

When attempting a bulk edit to change the assignee of issues in Jira Cloud, users encounter an error if usernames(not display name) and account IDs match for different users. This problem specifically arises during the bulk edit operation and does not occur when assigning users to issues individually through the issue view. 

Environment

Jira Cloud

Prerequisites

The issue occurs when there are users with conflicting/same username(not display name) and account ID, being assigned to the issues.

Steps to Reproduce

1. Navigate to the Jira Issue Search page and initiate a bulk edit operation.
2. Attempt to assign a user to the issues, ensuring the user has a conflict between other user's username(not display name) or account ID.
3. In the assignee selection dropdown during bulk edit, observe that the user is either not selectable or, if selected, an error message appears upon proceeding to the next step.
    - Error Message: “User <ID> cannot be assigned issues.”
4. When attempting the same operation in the backlog bulk edit, the user can be selected, but an error flag is displayed upon submission, indicating the operation was not successful.

Expected Results

The bulk update operation should successfully update the assignee for the selected issues without encountering errors.

Actual Results

An error is encountered when trying to update the assignee field via bulk edit, specifically when there is a username(not display name) and account ID conflict.

Workaround

As a workaround solution, assign issues individually to users through the issue view. This method does not present the same error and allows for the assignment process to be completed.