Shifting problem on the y-axis

Hi everyone

I’m really hapy with my k8400 and my firsts print were great.
But after if I printed the Groot Bust Sculpture from Thingiverse, my printer got worst print after print, the y-axis was more and more shifted, the x-axis seems fine (or at lease not so bad as the y-axis). I thought i had to make the XY-Carriage Alignment tweak, but i found this a little odd since my printer worked without shifting at the begin. So the problem could be an other. I did a check on the Motor for the y-axis and saw that the pulley was not aligned on the flat side of the shaft, which means that the pulley wasn’t tighten enough. i try to tighten it again but the SET SCREW wasn’t holding anymore when I tighten it too much. Now my printer work, but i don’t for how long =( (Probably the x-axis has a similar problem since on my last test-print the y-axis was right the x-axis just a little bit shiffted). I wanted to ask where i could buy (order) a new Pulley for my printer in Switzerland.
Best regards and thanks in advance

p.s. next time i will write in french or german … sorry for my poor english knowledge

Better oil the rods after and before long prints… If I don’t make em slippery as snot ones and a while the same thing happens. Ptfe oil is ideal. I apply it with a small sponge.

Kind regards