First things first: open the machine and pull out its guts.
On some units, the servo motor may also be held in place with hot glue. It should come away without much trouble — let me know if it doesn't.
The only slightly tricky part is fitting the circuit board back into the slots (as you can see).
Even if the arm is properly positioned, it's worth recalibrating so the software can fine-tune the motor position (not strictly required, though). For this you'll need Chrome or Edge (no other browser will work) and a cable to connect the machine to your computer. Then follow the steps in the video — once the test has run, the machine is calibrated.