The Oven Door Doesn't Shut!

We had a problem with an oven door that wouldn't shut last week. The oven was cleaned by Nigel on the Monday and the main oven door wouldn't close. Nigel didn't notice at the time but the lady called the office and we got him to go back to try and get it to close properly - the door was staying slightly open - but he couldn't get it to close fully. I went to have a look on Saturday and after taking off the door a few times, comparing it with the other oven door on the same cooker, I had just about given up when I spotted that the door was being obstructed by an oven tray. I moved the tray and the door closed! On this particular model of cooker, a Delonghi, it has an oven tray that is designed to be put at the bottom of the main oven and it fits in there very nicely; but if you put it on the side racks of the oven it sticks out just a little. I'll bring this up at our weekly meeting as we need to make sure the Team put the oven trays back into the oven in the right places!