Always get AESDecryptor with MAC: MAC check failed errors

[AlKoch]

Hello,

I am having a consistent set of errors when backing up specific files. Here are the details:
I am using "Backup"
The target is an external USB Drive
I installed the S.M.A.R.T batch file to have the drive checked and it's OK.
The errors only occur on "larger files", apprx 1GB and up.
"Smaller" files don't trigger any errors.
I request that the files be checked after copy.
If I do not compress and encrypt I get CRC errors
If I do compress and encrypt I get AESDecryptor with MAC: MAC check failed] [ERROR] on these "larger" files.

There is nothing wrong with the source files (they are videos that play just fine) but I cannot get them backed up to this external USB drive. (I have changed to a different USB port but that didn't eliminate the error.)

Can anyone suggest how I can track down what the problem is.

Thank you.