Certo Six overlapping frames

[Shugpug]

Any ideas on how to stop the frames on my new to me Certo Six? It was CLAd before purchase - is it as simple as print two and a half strokes on the winder..?

Frustratingly, it's not every frame, so it is clearly something in doing (although I guess it'd always be something in doing on a fully manual camera!)

 

[medwaygreen]

Not used this camera,but, the manual has a few do,s and don'ts on loading and firing the shutter. Manual here.

https://www.cameramanuals.org/pdf_files/certo-six.pdf

 

[Shugpug]

Thank you - looks like a modern film/old camera issue. Is read that before I got the camera but had forgotten the addendum...