jcb 535 steering fault?

ive a tricky one here.
our 2003 construction spec handler is stuck in 4 wheel steer, weve had jcb dealer to it and tried various solutions inc new control box, prox censor. etc
fuse just keeps blowing and all 3 steer mode lights on dash.
after mwchanic gone wheels slightly off line now.
we changed battery for new. after that we noticed the fault.

any ideas welcome.

thanks in advance.
dan