I agree with a lot of what David has said.
I experience similar issues as well and have found a few extra points in my research.
1 – David mentions engaging the glutes. I feel that as I descend, it becomes harder and harder to keep them engaged which results in my pelvis tilting incorrectly. I read an article that coached to focus on squeezing the sphincter. Kind of weird and funny, but I can see the value. The sphincter is almost at the most center and deepest point of all the glute muscles. If you focus on squeezing that – you almost can’t help having all the surrounding glute muscles also engage.
This doesn’t necessarily create more room for the femurs, but it helps keep the pelvis in the right position throughout the whole movement. Which keeps you from LOSING room. Other factors, at least for me, I think are still getting in the way.
Wider stances definitely help me.