"You can’t copy “_IMG_3815.JPG” because it has the same name as another item on the destination volume...."

It sure sounds as if you have two (or more) files on the NAS whose names differ only on the capitalization - like

“_IMG_3815.JPG” and “_IMG_3815.jpg”.

The default on the mac is to use a case-insensitive format, which does not allow for the above.

What I'd do is to make a little script to traverse the directory tree you want to copy in the NAS and look for this kind of situation. In a first run, I'd just have it write out the conflict cases.

I have to run now, but if you need help with this let me know. Later today I could have a look at it.

Ok, here is a first attempt. This version is not perfect. It may yield false positives, in case there are files with equal names in different folders, but it may be enough if the number of repeats is small.

What it does: it looks at the directory tree below the start folder, list all the files and print only those that appear more than once (in a case insensitive comparison). It has two defects:

1) it does not say where the repeated files are (but see (*) for a solution for this);

2) it will count as a repeat even if the files appear in different folders (if there are too many of those "false positives", let me know and I'll try to improve this; if there are only a few, it should be ok)

How to use:

1) Copy the following line and paste it somewhere where you can make an easy edit:

find <<start>> -type d -exec ls {} \; | tr '[:upper:]' '[:lower:]' | sort | uniq -d > duplicates.txt

2) Replace <<start>> with the pathname to the folder in your NAS where you want to search

(if you don't know how to do this: open a Terminal window and just drag that folder there; then copy and paste it so it replaces <<start>> in the line above)

3) Copy the modified line, paste it into Terminal and press Enter. What a little (it may take a few seconds or maybe more, depending on the size of the directory tree). A file named duplicates.txt will be created (in your home folder unless you change the directory in Terminal). Double-click it and see the names of the "duplicate" files.

(*) To actually find the duplicate files, you can issue this command in Terminal - replace <<file>> with one of the names you get from the duplicates.txt file, and <<start>> as above:

find <<start>> -ilname <<file>> -print

Yes, I am aware of the limitations of my proposed solution. I did not explore this very deep, and I am sure one can improve it. That is why I spoke of "false positives" - they are precisely those files with the same names, but in separate folders. I was hoping that there might be only a small number of those, and they could be easily distinguished from the real positives.

I will think a little more about this and hopefully I can give a solution 2.0 without the above defect.

Wow... it was actually *simpler* to do it right the first time...

Try this version:

find <<start>> | tr '[:upper:]' '[:lower:]' | sort | uniq -d > duplicates.txt