Starting with the cylinders around minor axes, your work here is generally quite well done. You've varied your rates of foreshortening a fair bit over the course of the set, and you've been very fastidious in checking the alignment of your minor axes, catching even fairly small issues that could have easily been overlooked, leading to a risk of plateauing as we get into that "good enough" territory.

My only concern right now is with your ellipses - they're okay, but they do tend to be a little hesitant and shaky at times, which suggests to me that you're not applying the ghosting method in its entirety. It's not uncommon for students to become less conscious of whether they're following all of the aspects of the ghosting method, and to gradually slide back into drawing the marks by instinct. For the purposes of this course, it is important to ensure that you're applying the approach - especially when it comes to ensuring that you're executing your marks confidently. Additionally, be sure to draw through your ellipses two full times before lifting your pen, and don't lift your pen in the middle of the process. I'm seeing quite a few spots where you draw through the ellipse one and a half times (but not the full round), as well as cases where your pen kind of comes off the page, then drops down again, resulting in many start/end points in the ellipse. This last part, I expect is part of the general hesitation.

Continuing onto your cylinders in boxes, there is unfortunately a notable issue here - though not one I'll be requesting revisions for, just something I want you to be sure to apply yourself going forwards. This exercise is really all about helping develop students' understanding of how to construct boxes which feature two opposite faces which are proportionally square, regardless of how the form is oriented in space. We do this not by memorizing every possible configuration, but rather by continuing to develop your subconscious understanding of space through repetition, and through analysis (by way of the line extensions).

Where the box challenge's line extensions helped to develop a stronger sense of how to achieve more consistent convergences in our lines, here we add three more lines for each ellipse: the minor axis, and the two contact point lines. In checking how far off these are from converging towards the box's own vanishing points, we can see how far off we were from having the ellipse represent a circle in 3D space, and in turn how far off we were from having the plane that encloses it from representing a square.

That leads to the point that you're missing - it appears that pretty consistently across this set, you've extended only two out of the three sets of edges of your boxes. This leaves us nothing to compare your minor axis lines with (which themselves should have been extended farther back as well), and leaves us in a position where little errors can accumulate and "hide" in the area you're not checking. So, being sure to extend those edges (specifically the ones you missed were those running along the lengthwise direction of the cylinder) as well, and to draw your minor axis lines back just as far.

Be sure to practice in this manner going forward, so you can continue sharpening your instincts in regards to judging the proportions of your boxes as effectively as possible. I'll go ahead and mark this challenge as complete.