Hey IDWT ,
The oil was In the pit . It's a well sealed pit with no sump and I had to have it sucked out by oil removal specialists. When I arrived there was only enough oil to cover the pump left in the tank with the lift Sat on the buffers . Its only a two floor job with about twenty foot of rise but I had to put nearly 400 litres ( 100 us gallons ? ) of oil back in . Only removes about 80 gallons from the pit but the one next to it ( it's one of a pair ) has low oil level so I think they had some issues before and never replaced fully .

I considered a slow leak but the guys who work in the store say they used it the night before and it was fine , not noisy coming in to top floor etc...

What really throws me is the walls are whitewashed and I expected to see splatter of some description on the walls indicating which side went but nothing . It's almost as if someone has just scooped the oil out of the tank carried it downstairs and poured it in the pit . Surely if a seal blew it would have made some mess , even if they are inverted pistons ? The oil wouldn't spray straight down ?

Here's the other thing that doesn't ring true. The service guy says when he got there it was about mid shaft (10 ft ) up . He went to the machine room to hand lower , that's when it , in his terms 'dropped ' . But when he went back downstairs the trapped passengers had removed themselves and left the scene . Now , if you had been stuck in a lift for an hour and then it 'dropped surely you would hang around to complain , even ring a lawyer etc.. these people were never heard from again .

My only other theory was a slow leak the night before it only had just enough to make top floor , I know they always park and lock it top floor overnight and through the night the leak got worse . The first run of the morning people got in and a mixture of the remaining oil and some air was enough to let them take off .

These are ten year old schindler controllers , you would have thought they had low oil protection ?

Nothing about this job makes sense . It's part of a large national contract that we have just taken on , I'm two weeks into a new job new company the contract is fully comp . I'm getting pressure from the store to reinstate the unit as it's there busiest time of the year . I have dug my heels in and said I won't until I can either seen the cause of the leak or conducted every safety test possible . Have done a 200 % static test , will do a full load test on Monday and test the rupture under full load ..if that all passes, and I'm sure it will as full load won't be 200% of empty car static , then I'm going to have to turn it back on and file this under the ' what the hell ' category .