Copying files to NAS gives Error Code -50 "Error in user parameter list" I had a cheap NAS that I was using that would give me an Error with code -50 whenever I tried to copy certain directories of files to it. At first I thought it was just the NAS device. Recently I bought a Drobo 5N hooked it up to my network, now I am getting the same errors for the same folders which makes me think it is an OSX issue.

Has anyone seen this before and how do I fix it?

My debugging steps:

I have tried the same process from two different computers and both give the same error. 

I have tried copying the files to a local drive or another DAS and they copied fine.

I have created an isolated network with a small switch and just my computer and drobo plugged into it and the same error occurs. 

I also have tried through 2 different switches and through just a Time Capsule but the error persists.

Any ideas?
The problem for me was that there were several invisible .appledouble folders within the folders I was trying to copy.

These folders are written by OS X for compatibility with Apple Finder Metadata with some NASs but are safe to be deleted (at least in my case). I just removed them all and everything was back to normal.

You can automate the process by typing the below into terminal when your pwd is the external drive. Please only do this if you are comfortable with the terminal - otherwise you could end up deleting important things.

find . -name \.AppleDouble -exec rm -rf {} \;