Interesting. Really hope others chime in after looking at how the wick is placed both for the ones that work well, and not so well. I'd expect really thin juices to be less affected.
A little below the holes doesn't appear to be a problem. What is, is when the wick is so far down, and or twisted to the side that it creates a sharp bend.
Yep mine are down far enough that the wicks are pointing at a 45 or worse of an angle towards the wick hole. And I use a 50/50 blend so it doesn't wick as good as it could be.