Position Y-axis shifted

Dear Forum,
After a few months I restarted the K-8400 to print. Now the Y-axis appears to be “shifted”, at least when the printer goes to home position, the motor keeps making noise to move the extruder while it is already in home position, it concerns the Y-axis, the X- and Z-axis go nicely to the home position (tried out with manual control). Now I have to say that the printer started well but after I started the print job via the SD card, the printing did not go well. When printing the first layer, the printer paused for a fraction of a second with each movement and resumed. Now I was able to stop the print job but did not turn off the printer so I pulled the plugs. And then the above problem came. Oops, I did something wrong. Who can help me?
Greet Auke

Problem discovered. The pulley of the engine is loose, how is this possible after all the years?
Greet Auke