Glad you had a breakthrough.
Get leaned over a bit more in the descent. See your back angle on the way up? It should look more like that on the way down. Reach your butt back at the start and point your chest at the ground. It'll keep you midfoot throughout the rep, and keep the knees in place at the bottom.
You could do with bringing the stance in slightly as well.
Lifting shoes should be your next investment, if possible.
Good luck!