The client stopped seeing the folder.

Hello! I don't understand what's happening with the folders... I've been using Mozilla Thunderbird with this setup for a long time. I had a RedMine folder and a filter configured to move messages from the Inbox to it. But recently, the filter stopped working because it couldn't find the folder on the server, even though I could see it in the folder tree and in the web version of Mail. I deleted the folder and created it again. I enabled the filter, and the messages moved, but they weren't moved to the new folder, but to the one in the Trash, and the new one remained empty. Yes, I restarted Thunderbird, and messages started moving to the new folder, but I don't understand why this happened in the first place—why did I have to delete and recreate the folder?