Bob, I've created a second attachments directory (/attachments2) and made it active, all new attachments will go there. You can backup /attachments, then not have to do it again, no new files will be added. It's not a good idea to have 55,000 files in one directory, makes it difficult to do backups, and also can cause problems with file management. FileZilla and Ionos file manager both list 55,300 files in /attachments, while admin attachment settings and PMA show 57,184, that's the actual number of rows in smf_attachments. 55,300 is probably the limit for your ftp server (it's more commonly 9,998), it's a configuration parameter on the server and can be changed by host. The files are all there, you just can't see the remaining 2,000 or do anything with them.
Also restored your custom registration agreement from 1.1.21 install.