Can't delete OR chest (Avast Free 13.12 for Mac)

I’ve got a few flash drives worth of my old personal files from work computer. When I plug them into my Mac and scan them with Avast Free 13.12, some of them show infected files - but Avast can’t/won’t delete OR chest them. I just get the message “Delete Failed” or “Chest Operation Failed”.

I have read/write access to the flash drives in question so I’m flummoxed. How do I proceed when Avast can’t do anything with the infected files it finds?

Thanks!

Avast Mac Security https://forum.avast.com/index.php?board=5.0

I just get the message "Delete Failed" or "Chest Operation Failed".
Are they compressed / zipped archives?
How do I proceed when Avast can't do anything with the infected files it finds?
Right click folder / archive / file and delete manually