Unity freezes on playmode, probably related to lighting/rendering (possibly Xcode?)

Recently I updated to the latest patch (2017.1.3p2) (though I've been having this problem since the previous patch, and similar problems since 5.6.1 & 2), when I press the play button Unity becomes unresponsive.

Symptoms (using either completely new file or Unity's "Standard Assets Example Project"):

• Unity works fine with nothing in scene when play button is pressed

• Unity becomes unresponsive when a terrain is created (when play button is pressed)

• Unity works fine when cube is created (note terrain is deleted in this case), but only when mesh render is disabled will play works fine, if mesh render is enabled Unity becomes unresponsive (when play button is pressed)

• Unity works fine when cube is created (again note the terrain is deleted in this case), and when its mesh render is enabled, but only if the light component on the directional lighting is disabled, if light component is enabled Unity will freeze

To replicate

• create new project, or use the example project

• create a cube or a terrain (but I suspect anything will do)

• press play button

• enjoy an unresponsive unity

When Unity becomes unresponsive, I'm forced to force quit it from the Task manager, and I tend to delete the Temp file manually

I am not sure what is causing this problem, or where to look for for a solution. In the past (with 5.6.2) when unity froze like this (though I do not know if the two problems have the same cause) I was forced to go back to a backup when Unity was not frozen, copy/pasting work from the frozen version into the old one, to continue my work.

I am unsure if this would make a difference but I feel it prudent to mention. I am using OSX 10.9.5, apparently OSX 10.9.5 does not support Xcode 7.0(+), the minimum requirement for Unity, could this be related?

Any help would be appreciated :)

thanks :)