I recently purchased a Zhongyi Lens Turbo (m42>m43) adapter and a Vivitar 35mm f2.8 lens to go along with it. I'm pretty happy with the results, so I went for something a little more expensive: the Carl Zeiss 35mm Flektogon f2.4.
However, I haven't really been able to use it as it doesn't seem to fit the adapter correctly. I've included images below, but basically it will not go flush into the adapter like the Vivitar does. Both lenses have the exact same mount, m42.
Does anyone here know why this would be happening? I've checked for anything blocking the threads and there's nothing. There doesn't even appear to be any damage. Both lenses are in excellent condition.