Copying Files from one Network Share to Another, Location is unavailable

We have 2012 R2 Terminal servers with all the documents on file shares.
Recently we added a new drive to where users will save information. the Y:\ drive.
However when copying files there from another drive we get the following message:

Y:\ is unavailable. If this location is on the pc, Make sure the device is connected. If the location is located on the network make sure you are connected to the internet, and try again. If it still fails the location cannot be found or might have been moved.

The server is in dutch language so i had to translate the error message myself, it might be off a little. The odd thing though, it pretty much says the Y:\ is completely unavailable but the user is able to browse the drive. but the moment they try to paste a document there they get the error.

When rightclicking in the folder and Choosing the option New > Textdocument it is able to create the .txt file, i can also change it without problems. So i don't think its a problem with Access rights, the users have write permissions.

I have found this article online, and tried applying the registry key, but this was without success sadly.
https://techjourney.net/location-is-not-available-when-copying-moving-with-mapped-network-drive/
Also found
https://support.microsoft.com/en-us/kb/2019185

but the other suggested solutions are not applicable i believe.

I Hope someone can help me with this,
Kind regards