I know that when at coast or stopped it will shift into neutral, but this is while travelling at 60-80kph (40-50mph) sometimes even at 100kphAt times when coasting or at a stop, it will shift to neutral. Sometimes you can surprise it and the re-engage is rather abrupt. (Mine seems to have learned my driving style and seems to run just fine.)
If that's not what you're experiencing, I'd be concerned.
Would it be just a fluid change? or something more sinister