Reviewer autocomplete suggestion replaced by incorrect name after initial render

Summary

Reviewer autocomplete briefly shows the correct name, then replaces it with a different name, causing accidental wrong reviewer assignment.

Steps to reproduce

1. Open a merge request or issue
2. Begin typing a reviewer's name in the reviewer field
3. Observe the autocomplete suggestions

What is the current bug behavior?

The correct reviewer name appears in the autocomplete dropdown first, but shortly after another name populates and can be selected instead, resulting in the wrong reviewer being assigned.

What is the expected correct behavior?

The autocomplete should display stable, accurate results without swapping or replacing suggestions after the initial result appears.

Relevant logs and/or screenshots

Link to recording of behavior (GitLab internal)