Wrapped job problem

Hello

I have a problem, when trying to carve a text on a cylinder. Its my first rotary job and everything seems to work. The machine carves the first 2 letters perfectly aligned and then it starts to carve one letter a little bit up from the first 2 letters and then turning the other way when carving the next letter. So basicly it carves every letter in a zig-zag except the first two letters.

Does someone have any ideas, what might be the problem?

I`m using Heiz High-Z S-1400, winpcnc and vcarve v6

Martin