I have a LP Grand CV bought 6-7 weeks ago with one of the original adj 510's that has issues, but I haven't sent back yet to be replaced with the new reverse thread adj 510. And I have a month old LP/SL Grand with the newest adj 510. I run Nuppin's on both of them and have never had one come loose, probably because I do snug them down slightly. However, neither of the adj 510's will stay set for an atty that is taken off then put back on... they both have to be tweeked again as many times as it takes to realign the atty's position again.
The CV Grand will still go back to the spa for the reverse thread correction Rob offered, but I had pretty much decided I wasn't going to send my other Reos in for the new adj 510. However, a new atty I just got that won't screw into the regular Reo 510's will screw into the newest adj 510, so I might update them after all.