It is good news that the files seem ok when copied via the OS as long as you’re judging this in LR after previews have been computed.
Lightroom may use different USB functions to read data from the camera than the operating system does, so there could be something slightly iffy in the USB drivers that fails when LR is reading things its way but is ok when the OS is reading things the other way.
I always use a card reader when copying images to my computer, and I never use LR to do the copy. I do that myself in the OS because I can control the folder naming easier. I don’t have any reason to use LR’s renaming functions, so I’d rather just do it, myself. I don’t want to be dependent on any particular program’s idiosyncrasies to determine my naming conventions. I just leave my image names the same and put them in folders with the date and event/subject/location as parts of the foldername so I can find things without using LR keywords or LR naming scheme templates.