Not sure if it's on Tixati side, or on GTK side, but in Find & Replace Trackers dialog radio buttons only work when you click on the marks themselves, and not on their labels. In theory, this is contrary to all OS style guides published in last three decades. In practice, I've just removed a lot of dead trackers from a lot of torrents from various sources in one of my clients, and aiming at the small circle each time got boring fast.