The brachial plexus lays on top of the subscapularis muscle.
This is not a new situation and didn’t get to this place in a day so it can take time to resolve this situation.
You could have a rib or 2 out of place.
Did you do the mobilizations in the above episodes?
First you need to identify and address the cause of the situation. Until the cause is resolved you’ll chase symptoms.
There may be movement patterns or technique of skills which need attention.
Pretty safe to say it will require more than one session.
It took some time to get to this place.
There are things you can do daily to help keep things in check.
Consistency is key 15:00 minutes a day.
Then it will move to maintenance and checking in with it once things are in a better place.