Lines are being cut / engraved on an angle rather than perfectly vertical or horizontal.
See the photo below.
This is most often a result of incorrect belt tension or an incorrectly aligned gantry.
Check the belt tension by following the belt tensioning instructions in the assembly manual. It often only requires moving a belt by one tooth to differentiate between a tension that is too loose or just right.
Check the Gantry is correctly aligned. When correctly aligned, both gantry carriages should touch the top of the chassis at the same time.