Upload & Sell: Off
I don't think elapsed time changes the issue, if the buyer has not used the lens or gotten feverish about testing it fast. What it does change is that time has passed on and the seller sees the deal as well embedded in the past. What works best is some arrangement, i.e. get back within a week or two if you find a problem.
Paul, as there is at least a sense this is not clearcut, perhaps just sell it as is? Your standards are most likely higher than many, and it is important to know this, a matter of self awareness...also, lens problems and 'performance' if you will, follows a gradient, often quite broad - Roger Cicala has produced data on copies of specific lenses showing this. This one has visible issues but is not that bad to render it unusable, and your expectations overlap with the design induced output of the lens.
'Zeiss ZA lenses are made and tested by Sony, AFAIK. Only the design is approved by Zeiss or something similar.'
A very interesting story, lots of secrecy and doubt...
I don't know, the truth is out there somewhere...I will say this though - I sat through a video of a presentation by one of Sony's lens designer, young bubbly guy but very self-assured - who continually referred to 'the things we at Sony tried' in developing the design of the new ZA 50/1.4, no mention of Zeiss and this was very detailed design discussion - where to place elements, type of glass, nano coatings, prototypes, etc. It was followed by similar talk re the new 70-400II, same approach..
Zeiss was nowhere in the picture that was portrayed and the first person pronouns got a work out. It had a ring of truth about it, but who knows for sure?