I switched to Thunderbird 115 Supernova a couple of months ago. All was well for some weeks, but then a weird problem developed. I've always used Group By Sort, a huge help in organizing my endless flow of email. But now, when I enable Group By Sort, Thunderbird '''randomly mixes new and old messages''' - the list shows recent messages from 2023, then skips to 2022, then goes back to 2023 again. (See attached image.) I can't see any pattern to it. This problem affects all my email folders and sub-folders. I've tried all the obvious things - changing sort direction and column, using Repair Folder from the Properties dialog, etc. My only fallback at this point is to use Unthreaded view, which seems to sort correctly. Needless to say, this is incredibly annoying. I was hoping Supernova would improve my life, instead it seems to have broken one of my favorite features. (My last resort will be to revert to pre-Supernova Thunderbird... if that's even possible.) I've searched up and down the Internet, can't find any discussion of this problem. Can anyone help with this?