We are in 2024, entering into 2025, and most people still suffer from this ridiculous error, even after enabling long file names in GPEdit and also in the Registry.
To get around it, use ROBOCOPY
Open a command prompt as administrator
cd into the directory you want to copy from
know the path to the directory you want to copy the files to.
execute the command
the format will look like this: robocopy . “D:\DestinationDirectory” /E /COPYALL /R:0
robocopy . means robocopy everything in this directory and its sub directories
this will copy everything from the synology folder that is connected to your synology, and it will place it into JBOD disk 5 (change the paths to whatever you need for you)
By default your MTU is 1500. Here is how you increase it to 9000 to enable Jumbo Frames, with no network impact. It will speed up your system because it does not have to repeatedly send the header info on every small packet.