Sorry, I meant Macbook Pro.
I have been checking various forums to see if others have had this problem and it appears to be reasonably common. One of the solutions proposed was to use the terminal and input "dot_clean" followed by a space and the directory containing the file(s) involved. It worked a few times, but not always.
I was told also that this is due to a file created in FAT32 with data pertaining to the file in question, and the two did not always link up when being copied to another HD.
My MAC has 2 SSDs, the main one for iOS and programmes, and the other is for data.
I back up both, that is not the issue - it is when I have to make a copy of file(s) onto a flash drive or external hard drive. I've been told too that these external drives should be always formatted MAC OS not WIN - which I have done, but it has not helped.
I've noticed that it doesn't seem to be limited to any particular type of file either - it happens with jpeg, with .doc files, with pdf files, and so on.
I'l check to see if Alsoft Disk Warrior can be of help.
I may add too that this has not been going on for a long time, only a few weeks - it was never a problem before.
Thanks for your suggestions.