G-tech HT01 cordless hedge trimmer fault?

My HT01 trimmer will work only intermittently. I have to rotate it and it functions best upside down. I am an engineer and have stripped it down as far as I can and the fault appears to be a loose connection or a fault in the wire. I have had a meter on it and I can get a circuit across the switch but not always up to the head motor. I am unable to strip right down because I can't fathom how to strip the pushbutton that allows you to angle the head. If I could do this I could remove the wiring harness and check more thoroughly.