You might get several issues, if you are directly opening files from the server or a network location, to your machine and editing them. You might also get issue while saving then to the server. I think your issue is one of them.
This is because, several thing comes into picture while you are opening, editing, saving files over the network. You may face some network issues, firewall issues and mostly permissions issues.
So, adobe always recommends to save the file locally on the machine first and then perform editting and saving operations. once you are done, you can copy it to the network.
Check the below article just for reference.