When asking for technical help at the very least let us know the version of firmware you are running.Cliff's Calibration (Mapping) Guide is a MUST READ: http://www.vemssupport.com/forum/index.php/topic,97.0.html
I can't say that I've ever had a problem. But I could see that the metal might not take to the solder, what power is your iron? You may have to heat the wire a great deal to get the solder to take when you tin it. Once tinned the wire should solder to the pcb much cleaner.