Lofra - glass top hinge is loose and the top wont stay in the up position?

I have a 700mm Lofra free standing gas top and electric oven. My Lofra has been great for over 10 years however the glass top (covers the gas hot plates) has become loose over the years (now much worse after a service agent took it off and put back on again without tightening) and it has become dangerous as it falls down easily. I would like to know how to tighten this glass top?

Tanya
June 2015