Error -50 when copying files from external drive

What file format is the external drive - Windows NTFS?

Are you copying the files to your Mac, or trying to move them (dragging them and releasing while holding the cmd key) - because Macs cannot write to NTFS file systems, only read from them. And that includes file operations of any kind that make changes on a NTFS source drive.

So, copying may be writing to the NTFS drive (e.g., file metadata like modification dates) in a way that fails and the error kills the whole copy process.

Unfortunately I'm not familiar enough with NTFS drive formats on basic macOS to speculate further - I use Paragon NTFS for Mac because I generally need to write to the drives I use. So read-only NTFS drives aren't a problem I ever have directly.

A third-party NTFS driver is something you could consider if you are using NTFS drives all the time. The big names in that space are Paragon and Tuxera (though not the only ones), plus the open source Mac-FUSE project. On Sequoia you probably have to jump through a couple of hoops in Recovery Mode to allow third party kexts to run to use any of these (my Sequoia machine is the one place I haven't installed much beyond basic Apple-provided apps).