I've seen this a couple of times now and it's probably due to using an older version of Samba but I must say that I have not seen the problem for a few months so thought Win10 may have been patched. Try the following:-
In Windows 10 (or Win7 for that matter) in Control Panel and in Category view click on the text “System and Security”, then click on the text “Administrative Tools”.
Now double click and open “Local Security Policy”.
In the Local Security Policy screen on the left navigation tree, expand the “Local Policies –> Security Options” then about 2/3rd’s the way down the list you’ll see a Policy called “Network Security: LAN Manager authentication level”. Double click and change the setting to be “Send LM & NTLM – use NTLMv2 session security if negotiated.”
Then just press OK and close all of the open windows and then try again
In the case of Windows 10 Home, Local Security Policy does not exist; therefore make the change in the registry (use regedit).
Value Type: REG_DWORD – Number (32 bit, hexadecimal)
Valid Range 0-5
Default: 0, Set to 1 (Use NTLMv2 session security if negotiated)
Description: This parameter specifies the type of authentication to be used.