JCook

I'm using the same mac early 2015 and I've had quite a lot of issues with various tools and functions on affinity running very slowly and it often crashing. I wonder if it's simply a case of this particular spec of processor not coping with the demands of editing using affinity? However, I have noticed that performance is improved if you go to Preferences > Performance and bump up the RAM Usage limit. Maybe try that if you haven't already and see if it helps.