Hi, been following your problems from start, I have just installed my new premium 6400, did a lot of research on wireless systems and yale always came out tops for reliability and performance, cant see why your system is ready for the bin yet,
It seems you have exausted all lines of help and advice, but its usually the most simple things which causes the probs, have you tried wriggling the mains jack plug about or even just tapping the actuall control box while on, as you say after moving it back to its original position it worked for a short while, is it possible something is loose and not making contact inside control box.
What do yale say about this