Vegan mayonnaise never emulsifies? I'm beginning to think this whole "egg-free mayonnaise" thing is an extremely elaborate practical joke. I have exhausted all the tips Google has yielded, so I'm hoping someone on here has an idea what else I might be doing wrong.

Here's my basic recipe (variations I've tried are listed below):
1/2 cup soy milk
1 cup sunflower oil
1/2 tsp salt
1/2 tsp mustard
1 tsp vinegar
1 tsp lemon juice
Combine everything but the oil and whisk.
Add the oil in super tiny amounts, whisking like crazy each time.

Result: a very homogeneous white soup the consistency of water. There are no visible oil droplets. It takes about ten to fifteen minutes for the first oil droplets to appear, and a few hours for an actual layer of oil to form.

Soy milk and oil are both at precisely 28°C (82°F).

Things I've tried so far:  


with a blender.
with an immersion blender.
with an electrical whisk.
with a whisk.
with a fork.
on a boat. No, wait, that's Dr Seuss.
add 1 or 5 tsp of soy lecithin. Does nothing, but despite soy lecithin's supposed tastelessness, the result tastes terribly of soy.
have ingredients at 23°C (73°F) instead of 28°C.
use oat milk instead of soy milk.
use a warm water/soy flour mixture instead of soy milk.
use a different oil.
add xanthan. This makes a somewhat thicker, but terribly clumpy mixture that you really don't want to eat.
different blender speeds.
quadruple the amount of oil. This resulted in a much larger amount of soup.
continue mixing for ten additional minutes. Resulted in my hand falling asleep from holding the hand mixer for so long.


I am so very out of ideas. Any help is greatly appreciated.

Edit: tried a few more things and added them to the list of things that do nothing.
Well this is ... disturbing. Switching to a different brand of soy milk let me succeed on the first try. I have no idea what the manufacturer of my usual brand does to it, but after more testing, even water+lecithine works better than that brand of soy milk.

I hope it's okay to answer my own question. For anyone who comes across this via Google in the future: I tried two different brands of organic soy milk with the same official ingredient list and no visible differences, and one consistently produces mayonnaise while the other consistently produces soup.

Thanks to all the nice people who took the time to try and help me!