If your setup is as per the image at the top of the link you provided, then what happens if you bypass the RS485 line drivers and just connect the two UNOs together using the software serial pins?
I can see one potential issue with the example "Remote Arduino Sketch".
digitalWrite(SSerialTxControl, RS485Transmit); // Enable RS485 Transmit
RS485Serial.write(byteSend); // Send the byte back
digitalWrite(SSerialTxControl, RS485Receive); // Disable RS485 Transmit
If the software serial port library supports the flush() function, then it is better to use that rather than the delay() function. The flush() function will work with any baud rate, whereas the delay() function will have to be changed depending on the baud rate set.
The same applies with the master sketch too.