I've been noticing I'm having a hard time keeping my right shoulder blade depressed when I bench. Right as the bar touches my chest I feel it rotate ever so slightly out of position. Happens more if I let my arch fall at all. Not sure if it's a lack of mobility in my shoulder, or a muscle weakness that lets it move. Any ideas on what to look for that might help? I would attach a video if I had figured out how to do that yet lol. Do I need to upload it to a separate site first and link it?