A bug was reported by sok777 with the “dismiss all unread” feature, where topics are not untracked when the “stop tracking” option is checked. rubeno confirmed the issue and passed it on to the developers. The bug has since been fixed with a pull request (PR) as reported by kris.kotlarek.
Thank for flagging this bug! I was able to replicate the issue with your replication steps and have passed it onto our developers to take a further look into this. We’ll keep you posted on any updates. Your help in improving Discourse is much appreciated!