Hi Jon,
Thanks for the reply. I let our dealer have a look at it after the last gig we just did. From what I understand they removed the wheel and PCB, checked and cleaned everything and refitted it as no obvious faults were found. I think we will have to carry on using it, hopefully the problem is solved. I'm sure you understand my concern!
Of course, seeing as its an intermittant fault, I am well aware that generally in order to find a fault it has to be broken at the time! So we'll carry on using it and see what happens!
Thanks again,
Tom Scott