So part of the reason your lines are diverging is that you're extending your vanishing points and correction lines in the wrong direction still.

I put this image together for you quickly. It points to a few of the boxes that are incorrect (25 page 1 as an example means it's from the 25 boxes first page in the link). I also wrote up a quick explanation and created an example of how you can use your initial Y to determine which way your box is orientated and know which way to extend your lines. Remember that they should always extend away from the viewer.

Definitely don't grind, do address your mistakes and do draw boxes and previous exercises in your warm ups but grinding for perfection will just lead to burn out which can take up even more time than if you paced yourself well to begin with.

We don't expect perfection and neither should you, you're learning. We just want to see your best attempts, I'm going to be marking your submission complete and moving you on to the next lesson because your boxes overall have improved you just need to address your line extensions.

Don't beat yourself up for your mistakes too much, good luck in lesson 2 and I look forward to seeing your future work.