I have been having some shoulder pain when doing regular pushups, and easier forms of pike pushups. Harder variation of pike pushups (more vertical), aggravate it much less. Pushups with elbows tucked close by and hands closer to hips don't bother it, and wall handstands never hurt. For stretching, I have no pain when clasping my hands behind my back, yet if my palms are facing forward (ventral) , and I try to stretch my left shoulder backward, I get pain after my arm gets more behind my body. Never hurts to massage it. What the heck do I have? Is it just muscle imbalances and the joint out of position slightly?
Also, when I perform a butter fly cross motion without resistance I get a clunk in the shoulder when moving past 90 degrees.