I have experienced issues with the game as I am using OS sierra on my mac, but those issues have luckily been resolved. Although, both the VAB and the SPH have both been very laggy and jittery, and the problem seems to occur when I'm at ground level. My hypothesis is that the Kerbals that wonder around are causing the problem, yet no graphical changes I make seem to solve the issue. My mac is a late 2012 model with an intel i5 and 8GB of ram, so it's not the most high tech thing out there, but it's served me very well up to this point. Any suggestions or help would be fantastic. I love this game and have been playing it for a number of years, and I would hate something like this irritate me and stop me playing.
Not to worry I've just found the 'Hide space centre crew' button. I should really check these things before I start posting on the forum