We just released Mastodon 4.2.12, fixing a bug introduced in 4.2.11 which caused notifications for mentions from local moderator accounts to be dropped. If you updated to 4.2.11, we strongly recommend you to upgrade to 4.2.12.
Version 4.1.19 is not impacted.
Release notes and upgrade instructions are available on our GitHub Releases page: https://github.com/mastodon/mastodon/releases