Have you had anyone look at your technique for the deadlift or clean?
It sounds like a technique issue where it doesn’t show up on other elements/movements.
Currently, you may not be effected at a lesser number of reps or weight because your body is able to buffer the technique deviation at a lower number of reps/weight.
Your body buffers it until it can’t and there is warning just game over. Once you pass the tolerance level there is no going back until there is off time.
It doesn’t sound like a mobility issue flossing/rolling/massage isn’t hitting the cause of the pain so you don’t see an improvement.
Start with technique for the deadlift and clean.
Pro Episode # 21 – Pro-User Request Friday: Not Seeing The Change? You Need a Systems Approach.