OK, it seems to me that what happens is that if we don’t really take care (I’m sure you do, but maybe you, like us, have teenagers in the house that don’t) to thoroughly clean the blade properly each time, then whatever you have blended dries (you often cannot see it) somewhere around the blade spindle. Eventually this dried smoothie builds up and creates friction, which is what creates the noise and the heat, which in turn leads to the smell of burning. I have returned one NutriNinja for a replacement over this issue before I worked out what was happening. I now know it wasn’t faulty, just had this problem of buildup, which was burning because of the friction it caused, and tainting the flavour of whatever I was blending. So, now I take more care when cleaning the blade immediately after blending, really rinsing it thoroughly under the hot tap and every few days put the blade through the dishwasher. This has stopped it happening.