Military Press Form

If I keep my elbows “tucked” while pressing, but completely flare them when I reach lock-out, it seems I don’t get shoulder pain (been doing this for about a month… so that’s why I only say “seems”).

If I tried to keep the elbows tucked throughout the whole ROM: horrendous pain. If I let them “free”: pain. DB MP: pain and crackling.

Any ideas why does it feel ok if I flare at lock-out and use a BB, but hurts if I don’t flare or if I use a DB? Funny acromion shape?

History: I stopped benching after reaching 155 lbs because my shoulders hurt like hell, and after that, began doing BB MP, just to get the feeling my shoulder wants to shear from my body…and some more pain.