!!! Everyone tinkers at your own risk and responsibility !!!
I have repaired such constructs a few years ago. The problem is with the drive (drive and valve is only one part) and the brew group, this is almost identical in construction to the EQ300, EQ500 and EQ900. Is in my opinion a misconstruction of the highest quality, Siemens has now, as far as I know, more than 5 versions of the BG of the EQ9. That's where the problem lies, the hose, which pushes the powder chamber in one direction. After X-uses, it gets a kink (is still tight) and then the "force" is missing to press the chamber properly. Remedy can be obtained, if you simply turn the hose clamps on the BG up / down. Have once read a report, since someone has a rubber ring hingebastelt, which pulls the cup when driving down / turn then in position. Wonderful MacGyver trick, just looks like tinkering, but the end justifies the means.
But with the EQ500 there are problems with the drive. There the actuator and the valve are one component. The wise thing you see, there is a gear on top that controls the valves and the actuator. That's built so cheaply that the gear gets warped, is no longer round, it becomes oval. The little motor that sets everything in motion has no end of power. When it presses the coffee, you hear this, similar to walking through snow. And there's the problem, the motor has such a force that the gear gets deformed and then skips 1 or 2 teeth. Either new drive, the manufacturer collects a lot of money for such a scrap, or disassemble.
Disassemble the drive, remove the gear (with the wise thing), warm, make and press a wooden handle into it, let it cool, wood out, and then glue a piece of plastic 2-3 cm thick with the appropriate diameter, assemble and peace is. Pay attention to the correct position of the gears, they must be in a certain position.
When disassembling the device do not skimp on cell phone pictures. Is very helpful if the experience is missing. So no screw is left and the cables are also laid correctly again.
!!! Everyone tinkers at your own risk and responsibility !!!!