Users does not appear in the 'User picker'(reviewers) list while creating a PR in some situations

Issue Summary
Users does not appear in the 'User picker'(reviewers) list while creating a PR

Steps to Reproduce
1. Click "create pull request"
2. start typing user names to add team members to reviewers list

Expected Results
The users should be listed in the reviewers' search

Actual Results

The users are not listed in the reviewers' search

Workaround

Update:
Using the API call below, it is possible to add users after the Pull Request is created:
https://developer.atlassian.com/cloud/bitbucket/rest/api-group-pullrequests/#api-repositories-workspace-repo-slug-default-reviewers-target-username-put