Gary,
Please try connecting an external hard disk or SSD and copy a large folder to it from the internal driver or a SD Card. (at least 10GB.
I would love to hear that you can do that without any hanging or errors, but I have seen enough people on the forum with problems in this area that I am extremely concerned.
How do you find the lot number? I just got mine last week and it was definitely not a returned item. i7, 16GB, 512GB.
Kim