1:26 AM, Saturday June 20th 2020
Hey there.
There are a few things I notice about the 20 new boxes you've submitted.
You are still overshooting and undershooting as you mention, overshooting is preferred and you may find it helpful to lift the pen from the page rather than stopping on the page. You'll build muscle memory and learn when to lift to effectively stop the line where you want it to, this takes time and you'll figure it out as you progress so it's not a huge concern because it's ultimately something that just requires mileage.
There is something that I am concerned with however, and that is that it appears that you potentially get caught up in your personal objectives and individual steps and lose sight of the bigger picture in a sense. To give you some examples of what I mean let's look at your attempts at foreshortening here, you often end up with a case of 1 of the vanishing points being incredibly close while the others you keep as far away as possible. There are cases where instead of focusing on a set of lines and how they should behave you worry about the closest line to it rather than the entire set which is how you end up having multiple vanishing points, because you're not thinking of the box as a whole but the individual plane or line you're working on.
You still try to keep the majority of your lines as parallel as you possibly can which gives the impression you're not actively thinking about where your vanishing point is in relation to the box, because of this you get lines that aren't converging consistently or even diverge from each other in some cases.
Because of the nature of a vanishing point existing, lines may get close to parallel if the point is far away but they'll never diverge and instead always converge. Consciously creating your sets of lines with this in mind, with all of your vanishing points planned to create a box as a whole not just as a set of planes is the goal here.
With that being said I'd like you to draw 20 more boxes, I know it's tiresome but you really need to grasp the point of this exercise as it will be important as you move on.
Next Steps:
Please complete and submit 20 more boxes.