Seagate 4TB BarraCuda 3.5" SATA Internal Hard Drive, 5400 RPM

Cheap bulk capacity for a desktop second drive: a slower spindle than the 1TB and 2TB BarraCudas, and shingled recording, so it is at its best holding media and archives written once.

Copying several hundred gigabytes in a single pass will slow noticeably partway through. That is normal shingled behaviour rather than a fault, but it is also why the drive has no business in a NAS bay or a camera recorder.