Not as badass as my deltoid tear.... oh, wait... that happened running into a wall.
I think your coach is talking about your turnover, you might have great leg strength, but you're not putting one leg in front of the other fast enough.
I had the same problem with squats when I tore my deltoid, when I brought my arm up to the bar the pain was unbearable and worse when I actually put the full weight over my shoulders.
Also, I would stay to the sprints, or consider hurdling. My 100m PR is only 12.11 but I'm much more competitive in the hurdles thanks to some decent form and okay speed. My 200m is my best sprint event, but even in that I'm not great. (PR is 24.15.... shut up I know the 100m average is faster than my normal hundred lol, I accelerate through the race.)