I'm willing to bet the machine is
slightly out of warranty.
And I agree it's probably just a sensor. I would probably enjoy taking the thing apart and either bypassing the switch wiring or splicing the wires together. What have you got to lose? It's already 'dead.' Can you make it 'deader?'
I'm also willing to bet that for the charges to fix the machine, you can buy at least two new ones. An estimate would be nice, of course. And by "call an engineer" I assume they mean they won't be sending one of their own unless you pay for the trip and parts?
Unfortunately, the new machines will probably be less likely to last as long as your old one...they just don't make them like...<
Mannesmann Tally>
But, here are some possible sources for 'experimenting' and 'keeping you busy while the ladies have tea':
"Good luck, young Will Robinson!"