The pain is persisting because have not rectified the cause of the pain.
Using technique that is ” at least pretty good” isn’t good enough. Especially if there is already an issue.
Your body can buffer anything for a time until it won’t anymore and there is no warning its just done.
The pain and pain continuing a your body’s way of letting you know something is wrong.
The way you are standing may be an influencing factor in the situation.
You should not have pain while standing so if you do that is another place that needs work.
Have you watched any of the episodes about standing?
The hump is caused from your body creating slack within the system to complete the movement that you are doing. You make adjustments in position that you may or may not be aware of to go around other things that are restricting the movement.
It sounds like your hips are out of alignment.
Again if there is pain something needs to be addressed. If there is any pain caused its not a good situation and one that needs to be addressed.
It sounds like those areas are quite tight and it will take time for you to be able to hold the changed position. You need to work on it everyday for some time as it loosens up. New range with something means new responsibility.
Have you looked into any work on your psoas?
This could be an impacting element.