I had a real problem with my shoulder for a LONG time, like 10 years! I could never work my shoulders hard at all and the delts looked really small compared to my arms.

I tried lots of warmup, stretching, rotations, etc., but it didn't help.

Somebody suggested that I might feel better if I worked my rear delts harder, so I started hitting the bent-over lateral raises hard--until the weight and reps I was doing on the lateral raises was about the same as I was doing on dumbell shoulder presses.

It didn't just help, the pain went away!

I think that if your rear delts are not strong enough (muscle and tendons), then you can wind up stressing the shoulder unnecessarily when doing military and bench press.

Try it and let me know if it helps!