Rep for this ^^
As well as posture, it may be this kind of injury is related to the competitive element introduced to Eilte, by the multiplayer aspect. The tendency is to want a quick turn around in station, take the next flight, next trade run, without stopping to smell the roses, as t'were.
My view is to try to make a habit of taking a break, when landed in station. This should probably be part of the routine each time you land. Get up and make a cup of coffee or use a different mouse to navigate market screens so that you force yourself to stretch. Even role play it? And imagine you're out of your seat, in the station, while your ship is having maintenance done?
I've resigned not to be the one who wins any prizes for being first to Elite (that will be some young scamp with no issues of RSI) and take plenty of time, enjoying the journey not the destination. Good posture in seating seems essential too.
edit: Elite Shoulder is probably the gameplay equivalent to Muscular Atrophies or Bone Weakening, suffered by real Astronauts, living in zero G eg. on ISS. Don't forget "eye burn," from Cosmic Computer Screen Radiation!!
Roll a dice?? ....
Rules for Space Living