Transferring large folders of flac files

Hi folks,
I have about 1.8 TB of music stored in flac files, and the main copy is on an external hard drive. I want to make copies onto other external drives, as well as reload my MyCloud NAS. W10 file transfer always seems to time out, or stop for no apparent reason.

Is there a folder transfer product which would handle the transfer accurately without stopping?

Thanks for your attention.

C