I purchased several generic thumb drives at very low cost. I checked all of them with “chkdsk /f /r /s” and received a message for each one that “no further action is required”.
As a further check of these drives, I copied to each drive many gigabytes of ordinary files and folders. Even though the display showed that the copying continued to the end, the actual copying ceased midway with no error message after several gigabytes of files were copied correctly. This problem seems to occur when the copy speed rises from 5 to about 20 MB/sec.
I’ve searched the Internet and can’t find how to fix this problem or even any mention of this problem. Are the drives simply defective? Can they be repaired? Could it be defective firmware?