LAN/NIC problem

[amc2012]

The crosstalk is ON THE BOARD. If you improve SNR getting into the traces on the PCB it may improve just enough to get it to work.

No doubt.   There is an array of caps and resistors on the board near the RTL8211E chip; and lots of cold solder joints on the ones on my three boards. There are differences in these devices between the three boards... and some of the 000 values (devices that look like a resistor, but have zero ohms) are soldered straight across on one of my boards with cold solder joints !  I honestly think the problem is a cap or solder problem, if not on the RTL8211E chip itself, perhaps on the 'mods' field of resistors and caps near the 8211E.  

I hadn't even looked at how poor the soldering was on that chip on my board.

It's bad.