Printing issue striations

Vertex 3D Printer Vertex - Issues while printing
1

Hi all,
My printer used to work well and producing smooth prints, since some time I have horizontals striations in my print and it is worse and worse. Any idea where it could come from?

IMG_1530.JPG3264×2448

These striations are all at equal distance from each other.
Many thanks
Gill

2

This looks like Z wobbling. Check the flex coupler on the Z axis (see the [color=#408040]Wiki[/color]).