I had the same issue with a brand new 2T external hard drive, in my case the drive would systematically stop working when it reached around 750Gb data storage. I could still format it with gparted and it would be usable again but the problem is still there and I haven't found a fix to this fault yet, so I'm left with less than half storage capability. That said, worst case scenario you can't get a refund/replacement, you could try doing some tests with utilities like smartmontools(cross-platform) and badblocks(GNU/Linux) and hopefully solve it
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=== Update (01/12/2021) ===
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UPDATE: After disassembing, connecting the disk to the pc through SATA and wiping it (zero-fill,1 pass) the problem was gone, all disk space usable, no more r/w errors - along with the terrific slowdowns and frequent hangs - occurred during file transfer. So I put the drive back in its USB enclosure, formatted it and tested again, still works fine, so I suppose one can replicate this without taking the disk apart. From what I understand, [https://en.wikipedia.org/wiki/Disk_formatting|reinitializing] the hard drive allows the identification and correction of damaged sectors; sure it takes a while, but mkfs utility did the trick for me. On Windows there's a variety of free tools (most of them included in [https://www.hirensbootcd.org/|hirencd]) to diagnose/fix hard drives presenting software-corruption symptoms
I had the same issue with a brand new 2T external hard drive, in my case the drive would systematically stop working when it reached around 750Gb data storage. I could still format it with gparted and it would be usable again but the problem is still there and I haven't found a fix to this fault yet, so I'm left with less than half storage capability. That said, worst case scenario you can't get a refund/replacement, you could try doing some tests with utilities like smartmontools(cross-platform) and badblocks(GNU/Linux) and hopefully solve it