shift during printing

Hello,

We have shift during the printing like on the picture.

Sometimes the shifting is bigger ( 5mm).

Can you help me?

Regards

Check the set screws on the motor pulleys. There are 2 on each one. I'm thinking you have one loose..

Also be sure your rails are lubed

Seems that your printer requires XY Axis maintenance. 

Make sure that all steps from attached manual have been made.