Error code 100060 when copying files to Mycloudex2ultra NAS

I now get this error when trying to add files from my Mac or an external hard drive to my NAS. It started after I updated to Mac OS Big Sur. But this problem only happens on one mac. I have another mac that did not encounter this error and it was also updated to Big Sur. I reinstalled Big Sur but that did not fix the problem. I can copy files from my NAS to my local drive no problem. Everything crashes going the other way.

Any time I try to copy a file to one of my shares, it tries for a while and then the drive unmounts and I get the error. Then I am knocked off of any internet connection. I can only get it back after rebooting.

I am having the same issue with my PR2100 and it started around the end of December. I have the same problem with both my Macs. Have not tried down loading from the drive but good to hear it might work if all else fails a I have about 400 movies I am concerned about losing. Plex still functions well.

I chatted once with a rep and she suggested to be sure it is plugged directly into the router. That did not help. I hope to try chatting again soon when I have a few hours to kill.

I thought my unit might be bad but if you are having the same issue, I don’t think that is it. Maybe a Mac OS issue. I will keep you posted and please do the same.

Hopefully someone has a solution.

I also have the exact same problem writing to Mycloudex2ultra NAS.

I have found an inelegant workaround that at least works for me. Normally I wish to transfer say a months worth of photos and this fails with Error 100060. So, I first transfer a small text file or single photo. This transfers successfully. I then transfer the block of files I really wish to transfer. This then works and I delete the initial small dummy file.

Here is the solution I found. It is related to Norton antivirus not working well with Mac OS BigSur. Based on this thread on a Norton community, it is a known problem that is not getting fixed.

https://community.norton.com/en/forums/macos-big-sur-network-protection-hangs-traffic

I can copy files when I turn off my Norton Firewall Vulnerability Blocking. Not a great solution but it works when I need to do it and I can turn it back on when I am not copying files. I don’t have any auto file updates so I can use this solution when necessary.