There are other impacting factors as well.
Hydration impacts mobility quite a bit.

Identifying where the issue originates is key as well. Where you see the issue may not be where it originates.
Are you working up/down stream of your back? rotator cuff?
Pro Episode # 21 – Pro-User Request Friday: Not Seeing The Change? You Need a Systems Approach.

A lacrosse ball may be too hard if it is a tender area. The muscles aren’t able relax or absorb the work you are doing. Another great option is Yoga Tune Up Therapy Plus balls.
Sounds like you are going too deep.

Keep chipping away at.