CRC Error sometimes

During my daily backup I sometimes get a CRC and the backup fails. Some days it runs without error, other days I might get an error 5 or 6 times before it runs without error (it automatically retries every 10 min or so until it succeeds.)  I'm running Win10 and I've done a CHKDSK E: /R on the external USB 3.0 backup drive in question. It is sort of irratating since I have email notifications turned on (to make sure it actually runs successfully) and I get many notifications. BTW - the backup is auutomatically run in the middle of the night and there should be no other activity.

Since I don't have verification turned on I'm not exactly sure why it is reading from the backup drive after the backup has begun,  according to the log in the notification email.