Close-contacts are such rubbish fits. Sorry, but they are.
PLEASE don't look at a narrower saddle - you definitely do NOT need a narrower gullet, despite what others here say. They're looking at the saddle instead of the horse.
I suspect you have that most common of problems, your horse falling in a little behind the shoulder. And with foam panel CCs being non-adjustable, flocking-wise, your best option with this saddle would be either to use
(i) A wither pad, probably between saddle and saddlecloth would work best. Provided it's correctly fitted so it sits over the hollow, not pulled forward so part of it sits over the back of the shoulderblade, it should provide enough 'lift' to support the correct tree width and give you some wither clearance. There's no correct dimension for that, by the way, just so long as you have 'some' clearance right the way along the spine.
(ii) A graduated pad or 'riser', thicker in front than rear. Again, this needs to be fitted so it sits behind the shoulder rather than pulled forward so the front of the saddleflap rests on it.
In all of this I've assumed your saddle gullet width is correct, ie. Wide enough. It's difficult to see a shoulder angle in your video because it doesn't stay in one place for long enough. If you can I'd suggest you take a wither tracing and compare it with the front arch shape, bearing in mind for horses that hollow behind the shoulder you must look at the angles based on a straight line drawn between the downward curve at the top of the wither and external curve of the shoulder, rather than the angles in the hollows themselves. You're lucky with your saddle you can take the gullet out to compare angles.
Best of luck :)