Well, when you do a bazillion sets of anterior dominant, pushing and pressing movements that internally rotate the shoulder joint, and not very many sets, if any, of pulling, scapular retraction, and external rotation movements, you are pretty much asking for shoulder problems.
When you do so many movements that promote internal rotation at the shoulder joint, and not enough movements to balance it out, you decrease space within the joint around the acromion process, coracoid process, etc. and create conditions for impingement and pain.
If this sounds like you, quit doing every version of pressing known to man and do more rows (all variations), face pulls, external rotations, and trap raises. You need to strengthen the muscles that stabilize your scapula, externally rotate your shoulder, and help to hold your shoulders back and down (rhomboids, middle and lower trapezius, infraspinatus, teres minor, etc.)
Most gym rats just do not understand this concept. I have a client I've been working with who fits this mold and he also has back issues stemming from a multitude of other issues with his hips, pelvic position, etc.
As far as addressing his shoulder issues, we have cut out all pushing movements except for some light cable pushes to promote range of motion in his scapulae. We do soft tissue work all around his shoulder with a la crosse ball, multiple variations of rows being sure to focus on getting quality scapular retraction, ITY's, face pulls, and external rotation variations. Since doing this, his shoulders have begun to feel much better. Why? Because we are opening up his anterior muscles, giving his shoulder structure room to breathe, and finally are strengthening his posterior muscles that are needed to help balance out the shoulder joint and scapulae and keep things healthy.
As frustrating as it is to see things like this, it reminds me that there are plenty of people who need help with their training/bodies, and helping people with things like this is one of the most rewarding parts of my job.