Automated triage: Not a bug
Thank you for reporting this issue. This report is from a 2.3 release candidate and is over two years old. In the current version, the lightbox sidebar's reaction button uses the same in-page reaction handler as the full media page, and nothing since has confirmed the problem. If it still happens on the current version, please post a new report with steps to reproduce.
This is an automated assessment. A member of staff may review and update it.