Thick lines outside - Every 9/10mm on prints.

Hi folks. New here and relatively new to 3d printing so please be gentle!Printer - Ender 3Issue - As you can see from these prints attached I am having some lines occur on the outside of the print literally every 10mm like clockwork. This occurs on both 90degree and curved prints.I’ve read up into this and think it may having something to do with the z-axis? In terms of settings I have used my own and then someone else’s profile from YouTube and still get the same issues.The rest of the print is absolutely fine in terms of sturdy-ness. Please help!!

It looks to me like your z axis is slipping somehow every once in a while... you didn't mention your printer, but is the coupler between your z motor and screw shaft tight? if you manually move the z-axis up and down (with the steppers disabled) is there any binding? Maybe dirt or junk in the rails, slides, rollers? The fact that it is so regular suggests some kind of cyclical binding... a worn out bearing somewhere?

it can also occur on i3 printers where the two z-screws are not perfectly matched.
Or on an ender 3 because it's a great big steaming pile......, sorry (thinking out loud again) - because you only have one z-screw and the daft wheels on the non-screw side. can work loose or just not move smoothly enough.

knowing what printer you have, would help :-)