Over the years, I had several Nikkor lenses with loose elements. I just chalked it up to poor quality control. The lenses were bought new.
That's the price you pay for spot checks, as well as lower prices.
Over the years I have had several Nikkor lenses with slight wobbles in the front element too. Every time it has been with lenses I have purchased new and used for years heavily until the focus became loose and dry sounding. In all cases the situation was resolved with a lens servicing. I chalk it up to being so cheap as to not having a lens overhauled when it needs an overhaul. My techs over the years have never been surprised by the situation, nor were they ever unable to rectify the situation for the price of a normal lens servicing. I never got the impression from them that the situation had anything to do with poor QC... but it is an interesting theory.
I've never seen a lens that worked properly if the helical isn't properly assembled. Pick a brand, any brand.
If one side short it won't make infinity and one side long won't focus closely.
The late 5cm series E had sufficient travel on inner and outer heliciod threads to allow different (pairs of) entry points for wear alleviation. The close focus and infinity stops are independent of the heliciod, the E has a coarse inner for its 90 degree focus turn from infinity to close in.
But the focus adjustment is limited and needs a matching pair of entry points. It is like a Rubic cube difficult if you cant see the topology.
The problem my lens had was absence of grease it had migrated.
When the trial fit worked ok (collimated) on moon, l screwed on the name plate ring.
Id not recommend it normally but it works ok as a salvage.
Takes about 15 minutes if you retain original entrypoints. The only special tool is darning needle to align the aperture mechanism on reassembly.
I have found that the bronze springs on the lens mount can become flattened out, resulting in a wobbly lens. I use a small round nose pliers to give them a little extra curve to reduce the wobble.
To be clear, on my 5cm f1.4 lens the springs are on the lens (not the body). A TINY amount of pressure with a well-placed miniature screwdriver solved the problem (lens wobbling in body mount) perfectly.