|If you do want to transfer the files it is quite easy to do it "all at once" - just the waiting time for them to copy over.|
Go to any folder or file you see on the Flash Drive, give it one left click. Now hold the Ctrl key down and press the 'A' key at the same time. This will highlight everything. Right click any of the highlighted files and select Copy from the dropdown.
Finally make a folder somewhere to take the contents of the flash drive. Open it, right click and select Paste. Everything will now copy into this new folder. Ensure the contents look right before formatting the flash drive.
Check the flash drive out by making a temporary folder. If it is OK copy back your files and folders using the same approach as already given.
This is all "very" easy - it just takes lots of words to explain things with computers.
It is possible that your flash drive is on the way out.
Always pop back and let us know the outcome - thanks