Difficult to tell from pictures, but pin height looks OK. Looks to me like the taper/profile of the pin is a bit off, not enough taper to it. You may be able to compensate for it by changing the spring out. As I briefly mentioned in the other thread, the spring that came with one of my clones caused issues. If you have anything that is close to it lying around try some different springs. You could also wind a few different springs using the solid copper center wire from various coaxial cable.
Make sure your clutch is smooth, on both sides, and clear of small protruding edges it takes very little change to the clutch to alter switch feel, so just polishing or removing a slight bit of metal makes noticeable difference, go slow if you decide to do this. The plating is very thin so be prepared for the copper to show through, which really does nothing to performance.
When it is working properly it has one of the nicest switches of any mech I've used. The pointier pin in the photo below is pretty close to 1:1 the blunt pin clone needed a bit of tinkering to get right, but performs equally well after. Blunt pinned looks closer to what you've got, and was also the one I had to mess with to get it working. I have a good supply of springs and it really only took finding the right one to get it working flawlessly. Well I did slightly alter the pin and clutch, but mostly only smoothing polishing, and making sure it had a uniform surface.
Problem with the Subzero clones is availability, SOI hit the china sellers hard with threats, and most gave in. Kindbright sold the best of them, and I believe that is who made my copper one. Focale has a Full length Legendary clone, mine works exceptionally well out of the box, think its about $17 right now. I've had all of mine for a while now use them everyday with zero issues.
availability and how much energy you want to put into getting it working should probably be your deciding factor. You can probably solve all your issues simply by purchasing the $20.00 upgrade kit from SOI. includes silver plated pin, clutch, and 510 pin with nut. All of it fits in all 3 of my clones perfectly.
The legendary long mode clone Focal sells is actually quite nice, and very close to 1:1. the three different clones I have all parts will interchange. so your shorty switch should fit on the legendary which SOI charges $30 for.
Don't know your skill level, or your patience level so you might be just better off returning and looking for a different one. On the other hand you could just mess with the one you have until you get it right. Did quite a few various experiments with my black one trying to get the switch just right. Started out firing erratically and with a very stiff and long throw. Tried a thin spacer in the delrin cup and various springs, in between all this I had the same issue as yours (couldn't tighten all the way without it firing. in the end it was just a matter of a proper spring for it. I'd be surprised if a good clean/polish and proper spring would not cure yours.
As for battery length that shouldn't be an issue, the battery pretty much locks everything in place above the clutch, too long battery will simply not allow the cap to be fully seated
If you have a caliper or something to get accurate measurements I can make some measurements on mine and possibly further pin down your issue.