lately I've noticed some excessive rounding in my back during deadlifting. Maybe its because lately i've been deadlifting after a heavy squat or GM session. but even during banded good mornings i felt like i was rounding pretty badly. I do not feel like this is a form issue--I can handle 400 pretty easily with perfect form. Its only during maximal weights or when I am fatigued.

is this something you have to naturally accept when the weights get heavier or do I have a prevailing weakness? I don't feel like for many "deadlift greats" their PR looks much different from their last few warmup sets.

would it just be my lower back? I feel like I've been hammering my hamstrings all summer and have made a lot of improvement, so I have a hard time believing i need more hamstring work (I've gone from doing an assisted GHR to fairly heavy band,as my back rounding has continued). do you need a video for this? I feel like I always have a hard time analyzing specific weaknesses.