Very often when copying large files at the same time, they'd get corrupted along the way or give out errors. The simplest solutions is not to copy them all at once but there are a few things that can be done.
It could be a hardware issue, so you could check you memory sticks; it could be a bad RAM module. You could try out your RAM sticks, test them by switching them. Also, update your chipset.
You could enable the Write Caching option of your external HDD for better performance. This is usually the best performance choice for storage devices.
Access Device Manager, double click on Disk drives and then on your WD Elements, click on Policies, under the upper Removal policy section, select (dot) Better performance, if "Enable write caching on the device" is not checked, check it as well. Make sure that the "Turn off Windows write-cache buffer flushing on the device" is not checked, to prevent data loss, as your external drive doesn't have it's own power supply. Click OK and restart.
Make sure you always wait till all the files are copied and then always "Safely remove the hardware". It's possible that if you eject the WD external drive unsafely, that some of the copied files would be damaged.
You could also check if it's your external hard drive that's causing the issues. You could do it with the WD Data Lifeguard Diagnostic tool:
Or you could do it with the CHKDSK command. Connect your WD Elements, go to My Computer, right click on the drive, select Properties and then Tools and then Check now. From there choose the action you'd like to perform, including the option to fix file system errors and the recovery of damaged physical hard drive sectors. If both options are unchecked, the utility only reports problems found, if any, without fixing them.
I hope any of this will help you!
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