When multiple clients all stop accessing a single server, it really isn't likely that the clients (printers) are the problem.
Typically 027-516 means an unsupported SMB type, typically caused by using port 445 on a device that uses Netbios over TCP/IP (uses port 139).
But since the server appears to be the issue, it would imply the smb change you made to re-enable SMBv1 (required since your devices likely can't do SMBv2-3) got over-ridden by another Windows patch (This is going to happen again and again so it probably isn't worth the hassle)
Short version and the best workaround is to simply enable FTP server side using the same exact folder, then switch the printers to use the FTP path/user.
This way Microsoft won't change things on you, and the shares that exist can still be accessed by any client PC's (So if you have the folders mapped on client PC's, there won't be a workflow interruptions there)
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