I've been making mayonnaise for 50 years, on and off, ever since my mother starting letting me be the family cook. I have never had a fail/separated mayo. I started using a blender recipe, and about 15 years ago moved on (or, maybe, back) to using a whisk. 2 reasons: i had read that olive oil, which I prefer, sometimes turns bitter with the high intensity beating in a blender (I had never had this problem, but wanted to avoid it), and a dear friend had moved back to the area after living for a long while in France, and convinced me that it wasn't that hard. I didn't make mayo often, only special occasions, until I realized the awful ingredients in even organic commercial mayo. The one product that meets my standards for quality doesn't come up to my standards for taste (or price). So I don't use mayo often, but when I do it is homemade. I finally decided to try the ubiquitous you tube recipe with a stick blender, and avocado oil (see olive oil caveat above). 10 times faster. Maybe 20, as it takes me about 20 minutes to whisk everything together. But from the outset I could see that it wouldn't hold together. Today I went back to my Luddite ways, and whisked together another egg yolk, a bit of Dijon mustard, and dribbled the failed mayo in, whisking madly all the way. Success! But I'll save the stick blender for soups in future.