As a very long time user I know pretty much what to expect from SS. And this isn’t expected: on highlighting a couple of false positives in the Spam folder and then selecting Train As Good (as usual), Mail will–well, not hang, exactly, but become unresponsive. No SPOD, and Activity Monitor does not go red. But it just hangs. And the more messages I have selected before choosing Train as Good, the longer it takes to clear. I use force quit and then re-open. The issue has the feel of an AppleScript issue, but what do I know? Not much.