Squat related shoulder pain fix?

37 yo, 178 lb male, have been strictly following NLP for about 4 months with great results. I recently squatted 300 lbs which was a huge accomplishment for me, after a lifetime of chicken legs. Bench 207.5 lbs, DL 330 lbs, Press 122.5 lbs.

I reached my first plateau a month ago, dialed the weight back, continued and was able to push through to squat 305 lbs, but then started having bad shoulder pain during and after squatting, which has interferred with my ability to bench or press after, which is a big bummer. I really dont want to to stall out prematurely, and apart from this shoulder pain I feel like I'm on a good roll.

I can't find anything about this, in the blue book chapter on squats, so I'm assuming it's not common, but I do see other threads about it in the past, with a wide range of comments and advice but I haven't seen any responses directly from Rip. Is there a predictable alignment error that would cause this, assuming no pre-existing injury? I'm hoping to attend the SS seminar in August in Los Angeles, but could really use some advice before that.

Thanks!
Brent