I don’t know man, this looks pretty great to me! Everything is perfectly clean and I don’t see any “tics” or playing “out of beat”. Maybe my standards are low. Or maybe I like to see the big picture. Is the motion correct? Yes. Is there hand synchronization? Yes. Does it sound good? Yes!
In fact, given what we’re seeing here, it is likely that what you’re describing as “falling apart” is probably not falling apart to the extent you may think it is. When you catch yourself using phrases like that, try to be more specific and ask yourself what specifically you’re referring to. Is the motion changing? Is the hand synchronization changing? Is something else changing? Is nothing changing? I think we have a tendency to over-analyze tiny variations in our playing that might not be apparent to other listeners. If there are bigger-picture problems, definitely, we want to recognize them and fix them. But if there are just tiny variations that only you can feel, and which you won’t even notice in six months when these motions become more familiar, it’s good to recognize that things are working correctly too.
The only other thing I’d’ recommend is not really thinking of this as “two way pickslanting”. I know that’s our fault because this is how we originally presented this. But what’s really happening here is that you are using a combination of different wrist motions to play these phrases, and changing the “pickslant”, or moving your arm in different positions, isn’t really what’s allowing you to do that. You’re just changing the direction your wrist is moving.
For example, look at the first clip, the descending portion which starts around 13-14 seconds. Put the YT player into slow motion and look at the pickstrokes when you move from a lower string to a higher string to repeat the pattern. These are double escape motions. Meaning, from the arm position you are using for this portion of the phrase, you can switch strings in any direction. You don’t need to change the position of your arm to do that — you can just keep your arm in the form you are using here, and simply use two different directions of wrist motion, as you are doing here, to move to a new string.
So moving forward, I’d try that. Use the form for the lower half of the phrase, but see if you can play the whole phrase that way without changing the wrist / flexion extension (motorcycle grip) style motion you are using in the first half of the phrase. You may have to tool around with this a little to find the sweet spot. But just keep the arm relaxed in the form we’re discussing, and try to play the phrase quickly by moving your wrist, even if it feels a little sloppy or you hit strings you don’t mean to hit. You’re already doing it correctly on the lower strings, it’s just a matter of doing it everywhere.
Nice work here.