I know doorpumps can delete matter sometimes, so this is probably the reason.   I let the chamber depressurise until it almost turned into a vacuum... Maybe you could solve the problem by supplying extra oil when the pressure gets too low using a shutoff valve system.   I checked it, and I really like the conveyor trick you used, but even it can cause some problems (the petroleum often has trouble heating up when the igneous rock in the first chamber gets too cold, which