Windows 7: Windows 7 PC file copy fails one direction and works between 2 XP PCs

Small home office Windows work group wired network of 3 PCs. 1 Windows 7 Enterprice + 2 Windows XP Pro SP3 computers.
The problem is over year long - copying files from Windows 7 to one of two XP PCs doesn’t work, other direction, back from XP PC to Windows 7 works flawlessly.
With 2nd XP Pro machine there is no Windows 7 PC copy problems.
When copying from Windows 7 to third XP PC and after that, while still using my Windows 7 PC, copying the same content between XP computers there is no problem.

I managed with this Windows 7 quirk until now, when I changed lately my Windows 7 PC to new one, with rather different hardware and fresh installed Windows 7.
But again there is the same problem. Any ideas what is causing this and how to troubleshoot?

I guess it might be something how Windows 7 File Explorer initiates new file transfer session. To one XP PC it’s different, then to other.
When copying from Windows 7 PC between XP PC’s, then there are also selected safe settings.

Some more info, which might help to understand this error.
Very often (but not always) Windows 7 copy of files over 100 MB fails to one Windows XP Pro computers with error: "There is a problem accessing \\pc2\foldername. Make sure you are connected to the network and try again" Sometimes after several retrials copy succeeds to finish.

While there is the error, always opening second Windows Explorer Window and connecting to the remote computer works
That means - there is not any network failure but just Windows 7 Explorer copy failure.
Once after several retrials I received the "network error 0x8007003b", which doesn't seem to help troubleshooting.

Any ideas?