I think I found what the problem was. When setting up my original backup, I did not check, "Lock the destination to this external hard drive." When I plugged in my 2nd external drive I bet that it assigned it a different drive letter. Is this possible? I do all my work on a "master external drive", ...

I have an external hard drive (H) that all my working jobs are on. When I leave the office I put the external drive (H) in the safe (unlocked) that I use for fire issues. I have another external hard drive (K) that I use to backup H drive as a mirror backup. The past two times I have taken the exter...