All machines have quirks, the new ones have high dollar service calls and parts, the older machines are much easier for a person with basic mechanical skills to deal with. I would take a couple of pieces of art that is representative of the work I would be producing and hit the road for a test of the prospective machine. Older Advance machines work fine and hold registration, they are cumbersome to set up and adjust. Older Gauntlets are probably the best, but for $5k, you are not going to get much in the way ease of use either. Old ovals are fast and workhorses, the go and go, but registration is sketchy at best and flashing is tricky also. I would hunt the old Gauntlet as my first choice, then a Javelin or Lawson.
Regarding the center shaft bushing: some people have knowingly purchased machines from me with a sloppy top bushing, these machines satisfied the buyer's expectations on registration. Not every customer uses a loupe to check registration accuracy, these are T-shirts not the dashboard for space shuttle.
