These engines aren't usually easy to stall, it's just that when they do it's a lot more sudden than a petrol engine. We doubt it's your poor technique if you've been driving for many years, but you may possibly need to adopt a different style than before, by ensuring the revs are a little higher or maybe dropping down a gear more than usual. However, it does sound more likely to be a problem with the engine in our opinion so it could be worth getting a second opinion and asking a competent and experienced mechanic to not only inspect it, but also take it for a drive to experience the problem.