WormWheel Siemens Espresso TK56001. (STL).
This wheel is used inside the motor section of your machine. If your machine makes loud clicks and strange sounds the worm wheel is damaged.
Replacement of this wheel is not hard to do but Siemens Services team prefer to replace the whole motor unit. An expensive repair I can tell you.
Remark: Do not forget to grease the main axes and the teethes in the motor unit once you are busy with your repair. Use synthetic greasing products that do not absorb dirt.