my 2000 prostar 190 (single axle) had the same issue. Had the wheel rip off on the interstate, cross the median, and then bounce over all the oncoming traffic into the ditch (phew).
i would have to stop every hour or so on the interstate ramps to re-tighten the lugs. My buddies 1999 ps190 single axle had the identical problem (he lost a wheel too).
I haven't had a single issue with my new trailer, even after towing the new boat further in one season than i pulled my old boat in it's lifetime...so i'm not sure what they did differently.
2000 ProStar 190, 2003 ProStar 197TT