Hi, hope you're doing well :) congrats on completing 250 boxes!

Here are some of my thoughts:

Lines are straight and confident. Excellent use of subtle lineweight too. As a result, your boxes feel very solid.

Convergences on the whole are quite accurate. I've noticed you mainly have trouble with the lines that make up the inner corner, which is totally normal as it's affected by the accumulation of previously done mistakes. You can try this alternative method of drawing boxes which has you drawing the inner corner earlier on and see if it makes a difference: https://imgur.com/a/DHlA3Jh

To further improve the convergence of your lines, you can start thinking about the angles and relationships between ALL the sets of lines converging towards a certain vanishing point, not just one pair. This diagram may help you understand what I'm trying to say: https://i.imgur.com/8PqQLE0.png

Lastly, in your warmups try to draw bigger boxes. This will give you more practise in drawing longer lines with confidence, and it also makes it easier for your brain to engage in spatial reasoning.

You can try the advanced box exercises when you're ready to develop skills further :)