Shoulder Trouble

I have some shoulder trouble and am looking to see if anyone has had similar problems. I get a lot of discomfort when I do two exercises. The first is standing dumbbell curls, when I do this my left shoulder feels very unstable, and I can hear popping and grinding. The second is when I do dips, when I am at the top of the lift I feel like the bone of my arm is going to shoot through my left shoulder.

Now the weird thing is that I can press (bench, and military) and row (horizontal and vertical) without any pain (or at least none that I take notice of).

Anyone had this before and knows what it could be? I haven’t been to the doc, I trust them not.