On of the challenges when teaching is teaching things that have become second nature so much that you don't think about them anymore. It has been done so often, it is so basic to the task, that the muscle memory has long since taken over, and there's just no thought, no effort to the part anymore.
Which means that if you are teaching, it's a challenge not only for the student, but also for the teacher - and for the latter, it's actually a multi-part challenge.
Part one: Realise that you are doing something in a certain way, which your students are struggling with, because they are not doing it in just that way. This step becomes easier when you are aware of the fact that something like this may happen, and that you may not be aware of everything you do, and that there might be a small detail that you do that makes all the difference. Even if you know about this pitfall of teaching, though, sometimes part one will not happen, as you are concentrating too much on other stuff. This realisation, for me, needs to either have a large and looming problem which is too obvious to ignore or leave aside for later, or it needs enough time and free brain space for me to mull over what the problem might be, and then arrive at a conclusion. The latter sometimes happens only after a workshop has finished, and it hits me on the way home, or the next morning as I wake up. (Which tells you that these problems do stay with me, and irk me, and I really want to solve them.)
Part two: Find out what, exactly, you are doing, and how it differs from what your students are doing. That sounds easy, right? But this can actually be rather hard - see above, for things that have become so much second nature that you don't think about them anymore.
Case in point, not textile-related? A few days ago, we went into an indoor pool to teach a young man how to swim. Obviously you can only cover the very basics in just one session, so that's what we aimed for.
One of the very very basics is the fact that water offers little resistance to slow movements, and much resistance to quick ones. There's also more resistance, much more, if you have a larger surface area than if you have a small one. So if you want to push yourself into one direction, you go quick with your hands or legs, trying to press as much surface area against the water as possible, and to "rewind" for the next push, you go slower, with as little surface as possible.
Now, both the Most Patient Husband of Them All and me are "Generation Swimming Pool Boom". As we found out a bit later, Germany saw a huge amount of pools built in the 60s and 70s, and of the Germans between 30 and 50 now, almost 90% are swimmers (as in they can reliably keep over water and move forward for at least a few hundred metres). Swimming has been so normal for us, having learned how to do it as children, that this slow-fast-thing is nothing we'd think about. It is something, though, you have to experience, and then learn which part of the motion is supposed to be quick and which is slow. And there's more little details to the motions, things that are surprisingly hard to explain.
So part two means looking at what you do very closely, looking at what the students do very closely, and figuring out what the differences are. They might be as minute as reducing pressure by slightly opening your fingers at one point of the movement, something not blatantly visible but actually quite potent (it's what I do when I turn tablets when tablet weaving). As you've got to find the difference in a motion or a sequence of motions, this may take some time - which may or may not be available in a workshop or lesson situation, depending on how much of a "safety time margin" you have calculated into your lesson plan, and how the overall thing is going.
And then, of course, what follows is part three: Explain what you are doing, and teach this to the students. The explaining part, for subtle things, can also surprise you by not being straightforward; and then the students need to try the new method until they find the right motion, the sweet spot, or the correct amount of tension or pressure. This, too, may take more or less time, depending on how difficult the task is for the students, but if you are in luck, they can work on this while you are moving on to help someone else with their problems.
Part four, finally, is: Take notes of what you figured out, and taught, and how you taught it, for any future lessons in this regard. Once some detail like this has been identified, it's much easier to spot if that is a problem the next time around, but it's always helpful to make a note or two in the teaching script at the appropriate place... which can then serve as a reminder for you, not only about this particular thing, but about the fact that these hard-to-spot pitfalls may lurk somewhere else as well, and that you would do well by keeping an eye out for them.
So... have you made similar experiences? Have you stumbled over teaching something because parts of it were so second nature you had a really hard time passing them on? And did you manage to solve it?