The squat has never been my best lift and recently I’ve been doing a lot of research trying to find ways to improve it.
One thing I’ve noticed very recently is if I struggle to push myself out of the bottom of the squat I end up leaning forward and doing more of a good morning squat. I initially thought that this happened because my posterior chain was weak but could it be that it’s more of a leg weakness problem causing me to lean over?
Usually if hips shoot up first then it’s a quad weakness.
Front squats, close stance leg press, high bar squats, leg extensions, etc
Vid of heavy squat would be bestest for diagnosis. I think it has to do with how you get out of hole. I think knees shift back with both relative back and leg weakness so it’s a bit hard to point out at times.
I think that on top of weak quads, glutes could have something to do with it as well. A lot of people have weak glutes, plus movement patterns that don’t fully involve them. When your legs are bent like they are at the bottom of a squat the hamstrings are in a lengthened position which means that they can’t produce much force. By shifting into a good morning you are putting yourself in a position where the hamstrings can take over. If the quads were strong enough to extend the knees and the glutes were strong enough to extend the hips then that wouldn’t be happening.
Other than just looking at weak points, the other thing to look at is technique. If you have this problem to some degree even with weights well below your 1rm/far from failure then half the problem could be that you have bad technique.
If I was you I would stop pushing past technical failure because once you have enough weight on the bar you won’t be able to finish a squat as a good morning. Some quad and glute work would probably pay off too.
Do you squat morning in wraps? That is a good test for if your legs are causing the issue as they increase your leg output.
Look at what your elbows do. I’ve seen lots of guys that have high elbows in the squat that, when coming out of the hole, only get higher. This often puts force into the bar forward rather than up and back, which puts them in a good morning/high hip position. Make sure you’re driving your elbows under the bar coming out of the hole.
I’m not sure about that because I was having issues with that when I was getting back into wraps and it wasn’t an issue without the wraps. The thing is that wraps will make your knee extend faster so if you can’t extend your hips at the same rate you end up bent over.
I think the issue can be caused by multiple things. As Tasty_Nate said above, elbow position (as well as shoulder position) cause the squat morning as well.
The wrap test for me indicated that my quads were a bit weak, because it solved the issue for me. However, you may still squat morning due to one or multiple other issues (and even have strong quads). You may have weak quads, try wraps and still squat morning due to elbow/shoulder positioning.
Honestly until there’s a video or more statistics we’re all just going to speculate 
I’ve had a similar issue, for me it was poor glute and hip activation. My suggestion is squat with a hip circle band above your knees to cue you to force your knees out and active more glute and hips.