Problem copying to multiple drives

[Clinton]

Hi,
I make weekly incremental backups manually on 2 external SSDs from my laptop. I noticed that some files are not being copied over to one SSD - these are the files whose names have not been changed, but their contents have been. New files (with new names) are copied over without any problem.
This is not specific to one SSD, happens to one or the other.
Any suggestions as to what I could be doing wrong?
Thanks (for an excellent program!).
Alex

[cobian]

Perhaps the archive attribute is not set when the files are modified?