OK, I am confused. Before we send the guy down multiple rabbit holes, it'd be good to know what exactly he was dealing with being loose.
So OP, what exactly was loose? And did you remove it fully before screwing it back in? Can you loosen it up again? I don't remember the specifics on the Va Xenars, but some of these lenses can have the front retaining ring come off while the main body of the front group stays in the shutter block. Then the front element is loose. I think on Xenars the rear element is rolled into the brass mount but this could be variable.
Anyway, if the front retaining ring was loose and you don't recenter the front element properly to have it seat in the mount, things will be, well, not sharp.
Was anything sharp on the photos? In other words, was focus distance wrong, but parts of the image were sharp? If so, then you need to adjust the relation between the viewing lens and taking lens, and also adjust the infinity stop (luxury at this point, meaningless until you get the viewing and taking lens in agreement). If everything was soft, there is a problem in the lens elements, groups, and seating. No amount of messing with the focus system will get you sharp images.
The brass collet is underneath the plate on the focus knob itself. It allows you to set the infinity point on the focus travel based on a distant object or collimator. BUT, listen carefully, DO NOT go messing with this until you are certain where the problem is. If the lens elements are not seated properly, nothing you do with the focus knob will matter. If the viewing lens and taking lens are not aligned to show you proper focus on the screen, this will not matter.
There's an order to do various focus adjustments on a TLR to get it right. If you just jump into the middle, well, have you considered using your smartphone instead? And at this point, I am not convinced that there is ANY problem with the focus alignments and such; it could all be an improperly seated lens element or group.
The Xenar can be a great lens. A touch sharper than the Yashinon, a touch more open, in my experience. Sounds like you saw that in the first camera you had. Look, if this camera is also a turkey, send me a DM and we can talk about getting you a working, aligned, 12-exposure Va that will simply work from the moment you get it.